...or if there were any limits to the amount of games you could save.
Under normal usage, the limits of saving would sort of look like this:
Battery save: 1 save file per rom (assuming it actually had a battery backup at all); the actual number of 'saved games' will vary based on the actual game. Super Mario World (SNES) for example, allows 3 saved games within the one battery backup on the cartridge. So 1 file would allow 3 game saves in this fashion.
Save States: I believe RetroArch allows you to use 10 save "slots" (0 to 9) to create save states. If you are careful and keep notes on which slots are for what, you could have up to 10 saved game states for various reasons.
Typically when I have played a very difficult game, I would use Slot 0 to save whenever I finished a level and had good health, weapons, etc. as if I performed well. I would switch and use Slot 1 to temporarily save my progress after difficult jumps, mini bosses, etc. and if I take too much damage or lose an important item I reload Slot 0. This makes games like Ninja Gaiden or Castlevania manageable if I don't want to spend 80 hours of my life memorizing and mastering and old game with limited or no continues.