You are very right and I do find that with the most popular pairings in a fandom, or the pairings I have read the most, I do tend after some time to not require as much "couple development." For instance, at this point I pretty much buy John/Rodney and read and enjoy stories about them that don't really delve into the whole "this is how we got together" stage. Bates/Kavanagh on the other hand would require much 'splainyness for me to appreciate. :)

That being said, the how they get together is still my favorite part even for McShep or Wincest or some other pairing whose fanon, etc, I have internalized.

I've never thought about which stories I like the best in terms of when they were written but that's an intruiging idea. I think I like best the stories that come after season one of a show. So many times the earliest stories written don't hold up well over time in terms of characterization simply because we have so few points of data from which to extrapolate after three episodes, or what have you.