It got to a stage with me when I didn't play PSOne games for a long time. The cases took up quite a bit of space, so I got rid of the original cases and started using dvd wallets. Most of the games are in the wallets now, and some are still in their cases around the place. I've not had any problems. For me, it just saved space to put them in a wallet case.

With my PS2 and Ps3 games, however, they're still in their cases. I ran out of wallets, and to be honest... I prefer having them in the original cases with the manuals and stuff. My PSOne games are scratched to shit and so not worth much anyway.