I think my code to disable spawned coins after a while didn't work. You can probably imagine I way overscoped this game so fixing that slipped through the cracks. I was pretty brutal about capping spawns of and continually despawning mobs though. I left it running for an hour to test it and came back to thousands of coins and about 10 frames per second but it didn't crash.
Thanks for playing long enough for the lag to be an issue lol.