Default Custom ROMS Question

I've been flashing custom ROMs for a few years now and I've noticed something that I've always been meaning to ask about. At first a lot of ROMs are great. As daily drivers they work with very few if any bugs. Now I'm talking "stable" ROMs, not beta or nightly. But over time it seems like they become buggy. Does anyone else experience this? Even if you don't flash the updated kernel or newest gapps.... it just starts to get buggy. Anyone else experience this?