well two things happen when loading a game
1. most if not all my planets loose a class level, im not sure if this affects the tile count because i dont remember but i know when i went to sleep at 3am and awoke at 1pm my highest class was a 24 with full upgrades, while i left i had one 25
2. the planet maps changes, not big but its a bit annoying looking at your planet and having all your buildings floating on water.

either way its still better then any other game (not including the fallout series, sorry that was just to fun of a game ) i played.