Inventor shouldn't be prompting for a save on a file that hasen't changed. I'll give an example. I insert assembly1 into assembly2 and set it to positional rep1. I save assembly2 and close it. Now I re-open assembly2 and it asks me if I want to update. I say yes and now it asks if I want to check out assembly1. I say no since I haven't done anything to it. Now Inventor tells me that I need to save assembly1 and assembly2 even though I just saved them and the only thing I have done is open them. I think this is wrong and it can create a ton of unneeded versions of the assembly when using vault.