With some games it's a good idea, with most it isn't. If you want to talk about a game that uses some SSOP70 type roms that require a custom adapter to dump and can't be verified with 100% certainty then you might want to hold onto the board for a while. Namco System 10 where we don't know if some of the roms are dumped correctly, might not want to sell. If you are talking about a game that uses all common eproms that any programmer can read and it's running perfectly in MAME then it's a total waste to not resell and get something else needed. You can't lump every pcb together. It's pretty simple math anyways. I've probably resold well over 100 boards. Name 1 that is needed again.