Exodus 27:20 says that "the lamp [/menorah is] to burn always" but in the next verse it says that "Aaron and his sons shall order it from evening to morning". Moreover, 1 Sam 3:3 says "ere the lamp of God went out..." The NRSV footnote to this verse states, "The lamp in the temple burned at night. The lamp of God had not yet gone out, hence it was just before dawn" (The New Oxford Annotated Bible, p. 405). So, was the lampstand to burn "continually" and "always", that is 24/7, or just throughout the night?
In order to keep the lights burning required two functions: a supply of oil and a wick. Both had to be replaced regularly. Replacing the wick was sometimes called "trimming" the lamp.
It is not completely clear from Ex 27:20 and others that the light of the menorah was to be uninterrupted. If we understand 1 Sam 3:3 literally, then the Menorah was probably only burnt during the night. (However, many understand this verse figuratively referring to God's revelation.)
It is claimed that Josephus says the lamps were most burned during the night. https://biblehub.com/commentaries/exodus/27-20.htm
In any case, for something to be described as "continual", or, "always" in the sanctuary, did not require that something be completely uninterrupted; daily events were described as "continual". For example, the regular morning and evening sacrifice at the temple/sanctuary was described as "continual", see Num 4:16, 28:3, 24, 29:11, Neh 10:33, Ezra 3:5, Eze 46:15. The Kings allowance was also described as "continual" despite only being a daily delivery, 2 Kings 25:30, Jer 52:34.