should have searched a bit longer on the forums ... i found what i think is the answer from Ashley
...actually, you should be able to change the name of things and it will still work, since it doesn't save data by the names of items, it uses a hidden unique ID instead (so you can rename everything and it still knows where to load data).
If you add any new object types obviously they won't have any saved data, and if you delete object types then it won't load any thing saved for them. Similarly if you add layers or remove them etc. you might lose data, but if you don't make any such substantial structural changes it should keep loading just fine.