I think a lot of this comes down to personal temperament and whether you can be at peace with being "mostly" done, even if you might never be completely done.
Most of my player master set registries are nearly done, but might never really be done, due to a few pieces that may never become available to me. Or if they do come up, the potential seller might decide to only part with it for six figures, which is unlikely to work for me. Certainly my Master Mays set could come down to that, with 2 pieces left to find.
https://www.psacard.com/psasetregist...timeset/290520
I'm also just a few cards away from completing some other very difficult sets, realizing that I might never get there, either due to the last pieces never being available, or I might just not be willing to spend the serious cash required to land the final pieces, including:
1971 Bazooka Numbered (46/48)
1973 Topps Comics (23/24)
1954 Stahl-Meyer (11/12)
1953-1954 Briggs Meats (35/40)
For that matter, my quest to collect the full set of 1963 Jell-O Complete Boxes is almost certainly futile, particularly since I only have 6 of 200, and progress is glacial at best.
But in every case, I'm having plenty of fun collecting these sets, even knowing that my odds of actually getting to 100% aren't very good. Confession: I'm also not someone who lives and dies by getting stuff 100% done. I'm usually pretty okay with getting most things 90-99% done, moving the goal posts, and calling it done.
Why let perfection be the enemy of pretty darn good?