[A_perfect_lady]

Was he supposed to come back in “X” number of years, “X” set by humanity?

Well, the Bible does claim that he said there were some in that crowd who would not taste death before the kingdom of God arrives in its glory. So either there are some 2,000 old disciples quietly tottering around Israel today, or...

[editor-surveyor]

>> “Well, the Bible does claim that he said there were some in that crowd who would not taste death before the kingdom of God arrives in its glory” <<

.
The kingdom did come in its glory, at the transfiguration, and on the temple mount at pentecost, after his resurrection.

Read the Acts.

[Elsie]

So either there are some 2,000 old disciples quietly tottering around Israel today, or...

...your understanding of what 'the kingdom of God' means is a bit faulty.