Well I think paul is thinking nothing since he is dead. Many of His atoms have likely been reclaimed by other life forms and returned to the soil several times since then.If you accept the concepts of heaven and hell, then it is easypeasy to explain. In this context, lifetime is the entire lifetime of your spirit. Also known as forever. Therefore god's got infinity time to fulfill that.
Has anyone attempted to explain the whole ~"these things will come to pass in your lifetime"?
Life "time", it was called. Infinite beings don't need to take that into consideration, or even name the concept. Time is irrelevant to those who will be around forever. None of the words in their language would reflect any concept of time. And when addressing folks for whom that lack of time is an unknown, such as the aforementioned crowd, if JC was really saying he would be back at some point in infinity, he should have said so, rather than confusing the locals and creating generation after generation of followers who are absolutely convinced that he will show up any day now.
If there is a heaven, I wonder how messed up things are up there, given that things are messed up here rather horribly by all the misunderstandings the biblical god and his kid caused. If the dude is real, he can't omnipotent his way out of a wet paper bag. I wouldn't get your hopes up on the "living forever with god thing" if I were you. You might have to sweep floors or clean toilets for all of infinity, because of oversights in his planning of heaven.