I kinda made that decision in the early '90s.
I have complete sets from mid '70s to early '90s, however they were of all major companies. So ex. '89, I have Bowman, Donruss, Fleer, UD, Topps, TSC and so on. The '90s started the glut of just too many sets to collect!!!! So I added just 1 set my choice from early '90s to early 2000s, then hit or miss from then until now. Also, I collected both football and baseball at the same time.
Vintage Sets: I have some complete sets from the '50s to '70s, I have gapped a few years with reprints or Archives. I will continue to work on vintage sets through lot buying and trading.
Meanwhile, from the 2000s on, I will buy 1 factory set / year unless I have so many singles, I feel that I could build the set thru a few purchases and trading.
Hockey and Basketball, I've kept a few faves, but primarily selling and trading them off, plus all the singles. Non-Sports, I keep and collect anything, and continue to build smaller sets as they come my way.
So, that's my story.