I had a 3rd party ps1 memory card with like 120 blocks and it always worked fine. When I finally got a ps2 i put the memory card in it and lost all my saved data. Had Xenogears, FFVIII (last dungeon, some optional stuff ), FFVII (same as FFVII), FFIX (same as FFVII), FFT (all optional stuff done), some licenses in Gran Turismo 2, Xenogears (all optional stuff done), Street Fighter Alpha 3 (some characters complete on World Tour), Star Ocean 2 (mid game), RE2, and probably a bunch of shit I can't remember right now.
I was busy with my PS2 and didn't replay most of my PS1 games tho, so it wasn't so bad.