The Father's will, in these verses, is expressed in the subjunctive mood; the Son's obedience is expressed in the indicative.
In 35, eating/drinking the Bread/Drink (understood) of life is in parallel to believing. Likewise, coming (37) to the Bread for life is what those Galileans were NOT doing, believing (36). In 37, "All" (pan = the whole group--neuter--not part of the group) that the Father gives the Son "will come" (indicative). The question is, what is the Son going to do with his gifts from the Father? The Father's will is that the Son *should not lose" (subjunctive) of the whole group he has given to the Son, but *should raise" (subjunctive) it up on the last day (39). Further (40a) it is the Father's will that "pas", everyone making up the whole group, everyone looking to the Son and believing (Is this reminiscent of 3:14-16?) "should have" (subjunctive) eternal life (which, indeed, a person "has" (indicative) upon believing, according to 47, but let me not jump ahead).
This is the Father's will, but is it going to happen? Jesus answers that question in two stages. Firstly (38) he, the Son, came here "to do" (not to attempt to do) the will of his Father (38). So will he do what he came to do, or should we put a question mark over his obedience to the Father? Will he fulfill the Father's will? Jesus, himself, leaves us in no doubt: "And I will raise him up (indicative) on the last day" (40b). The Father's will, in these verses, is expressed in the subjunctive mood; the Son's obedience is expressed in the indicative. Accordingly, the outcome for the auton (him) who comes to (believes in) Jesus for life (44) is "I will raise him up" (indicative), and the outcome for those who for eternal life look outside of themselves to the sacrifice of Christ (54) is "I will raise him up" (indicative - no 'should'/'would'/'might' language here, but just the language of certainty, since the Son can be trusted to see to the Father's will.
Whatever might be said about the qualities of eternal life (zōē aiōnios, the life pertaining to "the age"--the coming age), here we have Jesus' own answer to the question of its duration. It lasts at least until the resurrection. By definition it is as lasting as the new age itself; it is as enduring as the life of the new earth where death will have been defeated. Everyone given eternal life when he believes will be gloriously raised at the eschaton.