Young's Literal Translation is a better reading in the English, and can be checked against the Interlinear. Each of the verses you have listed are phrased a little differently for each context. Though the overall thought is the encouragement of the saints, the context of each gives a slightly different perspective. All of these verses were encouraging those of the first century AD to patiently wait for the kingdom.
The context of Heb. 6:15 is of Abraham's patience as he waited for the promise of God.
"For to Abraham God, having made promise, seeing He was able to swear by no greater, did swear by Himself, 14 saying, `Blessing indeed I will bless thee, and multiplying I will multiply thee;' 15 and so, having patiently endured, he did obtain the promise;"
The Interlinear uses "καὶ οὕτως μακροθυμήσας , ἐπέτυχεν τῆς ἐπαγγελίας" or "and thus having waited patiently he obtained the promise".
The example was given in Hebrews so that those listening, or reading it in the first century AD could know that they would obtain the promise of the Lord's second appearance and wait patiently for it.
"so also the Christ, once having been offered to bear the sins of many, a second time, apart from a sin-offering, shall appear, to those waiting for him -- to salvation!" (YLT)
James 1:12 from the Interlinear is "Μακάριος ἀνὴρ ὃς ὑπομένει πειρασμόν" and in English is " Blessed [is the] man who endures trial...".
This is an example for all Christians of all time, but specifically for those of that generation that were facing the persecution that was about to fall upon them from Nero and from the Sanhedrin. They were going to have to endure that horrible tribulation and distress of which Daniel foretold (Dan. 12:1) and which Christ affirmed was to happen before His second appearance to them (Matt. 24:15-21). Their endurance of that trial was essential to receive the promise.
1 Peter 2:20 in the Interlinear reads in English "... if doing good and suffering you shall endure [it]..." In Young's Literal Translation it is
"but if, doing good and suffering [for it], ye do endure, this [is] gracious with God,"
Peter was telling them that suffering (enduring) when beaten, or wrongfully accused, or jailed for preaching Christ was to be expected as Christ had just done the same by dying on the cross for them. He continues in 1 Pet. 2:21,
"for to this ye were called, because Christ also did suffer for you, leaving to you an example, that ye may follow his steps," (YLT)
The promised land, the heavenly kingdom (anti-type of the promised land of Canaan) was still in front of them. It was not yet, at that time, fully established. After the cross (the anti-type of the Exodus) was a time of transition (40 years - anti-type of the wilderness wandering) to preach the gospel, to mature in the knowledge of Christ, and to endure the tribulation that had been foretold by Daniel, and confirmed by Christ (Dan. 12:1-2; Matt. 24:15-22).
That Christ had told them the days would be shortened for the sake of the elect was encouraging them to endure it... patiently waiting for the promised kingdom. Christ brought His everlasting spiritual kingdom with power and glory into full existence when He came back in judgment to destroy that temple in A.D. 70.
Once they had the promised land / kingdom they also had relief from the persecution as the power of the holy people (Dan. 12:7) was scattered. That was what they were constantly told to patiently wait for.
His second appearance in that generation was to execute judgment, and to establish His kingdom. Those first century Christians needed constant encouragement to endure the suffering, and the promise was the soon coming of the kingdom, and the judgment against those persecuting powers of Rome and Jerusalem.
"`Because thou didst keep the word of my endurance, I also will keep thee from the hour of the trial that is about to come upon all the world, to try those dwelling upon the earth." (YLT)
"Because you have kept the word of the patient endurance of me I also you will keep out of the hour of the trial being about to come upon the inhabited world whole to try those dwelling upon the earth." (Interlinear English translation)
About to come... when the book was written. Revelation was written approx. 66 - 68 AD, so the time of the hour of trial was to be shortly thereafter - not 2,000 years later. See DatingTheNewTestament
Again, the same command to wait patiently, to patiently endure the suffering they were warned of; namely the trial of the persecution that was to fall upon that generation. It is an example to all people of all generations since, but it was especially needful for them. The persecution of Nero was horrible, and can be read in several historical accounts. See: Persecution of Nero
As the New Testament books had been written before His coming back to them in the judgment in A.D. 70 against those who pierced Him (Rev. 1:7) and those who persecuted His church, the flavor of the future tense of the books becomes confusing to modern readers as we are not commonly taught the contemporary historical clues to look for in God's word. There are many time texts in the books.
We have to keep in mind that we are reading other peoples mail from almost 2,000 years ago, and that they were enduring events that many of us will never suffer.
All of the books of the New Testament, including Revelation were written to the new converts to Christ, who were promised His second appearing in that same generation in which He walked with them, spoke with them, and sacrificed Himself for all the people of all the world.
They knew He was coming back to them a second time, and they were all wondering when that would happen. They had to have the assurance and comfort to get through that trial and persecution. All of the books were constantly telling them to hold on, not to give up, to keep believing, to endure. They had to know that the suffering would come to an end soon in their lifetime.
They believed the promise of His coming. Christ told them repeatedly that He would come back with His kingdom (Matt. 4:17; 10:7; 16:28; Mark 1:15; 9:1; Luke 9:27), in judgment (Matt. 13:37-42; 22:1-14; 23:33-39; 25:31-46; 26:64) and in glory (Matt. 16:27; 24:30; 25:31; Mark 8:38; 13:26; Luke 21:27). They were patiently waiting for Him.
See my post "It's Not The End of The World, Part IX - The First Century Preppers" at ShreddingTheVeil . All ten parts of that series point out the time texts of the New Testament.
We have their example, that no matter what we face, we patiently suffer / endure what we cannot do anything about throughout our mortal life. We know that our promise is eternal life in heaven, and to place our citizenship in heaven (Rom. 6:23; 1 John 2:25, Phil 3:20; etc.)
Today, if we suffer for our wrongdoing, we should not be surprised. If we suffer injustice, we have the right to ask for that wrong against us to be corrected. However, in today's world, correcting injustice under today's political system grows less likely by the hour.
While we endure hardships, we are not having to patiently wait for the kingdom. That promise was already fulfilled in AD 70. Our patience is with one another, bearing each others burdens (Gal. 6:2), returning kindness for evil (Matt. 5:39-46) so that we are living our lives as ambassadors for Christ (2 Cor. 5:20).
They were patiently waiting for the "promised land" of the heavenly kingdom.
These verses are often being misapplied today telling Christians to endure / tolerate evil, and to remain silent.
But, we are told to resist the devil (James 4:7). We are not supposed to wait for God to vanquish evil practices, nor are we supposed to tolerate evil, sinfulness in those around us (Mark 16:17). We are called to stand up for God and speak the truth (Eph. 4:15; 6:11-20).
We are living our lives, running our individual race against sin, knowing that we have to endure this world in order to get to heaven. While we are here, we represent our Savior. We cannot do that if we tolerate (endure) evil by silently sitting down and doing nothing.
All bold emphasis is mine.