I have 35 XMB installed games and I only had to patch 5 of them. I have 20 PSN games installed and had to resign 1 of them. I have about 150 games on my USB HDD and internal HDD and so far I've had to only patch the latest ones. Almost all previous 3.55 patched games are working with their 3.55 patches still installed.
As I said in that other post, install 4.21REX and try out your games. And even if you do need to resign them it only takes a total of 5 mins and thats taking your time. If you do it quick you can probably resign them in 2 mins each game.
Think about it. If its from PSN then you DON'T need to patch them as ALL PSN games will work on ANY firmware above what its made for.