Is it a good idea to write a fanfic/story about an original TV/movie, but have it set years after they depart for some reason and have two of them meet seeing how he/she has had kids and they either fall in love or back in love? Becasue my story 'Affection' (check it out BTW) is just like that and I don't know if it's a good thing or a bad thing.
Writing is never a waste of time, and if you love something enough to write fan fiction about it, I say go for it. Don't stifle your creativity. As for the premise, that's the beauty of fanfiction, it can explore concepts that the source material didn't.