Sometimes, well it did for me Mostly why i never get to Attached to one Character, or you might have messed up an Installation, overall i does sometimes happen so do look out!
It varies from release to release, unfortunately. It depends on what gets changed, so sometimes really old saves that use defunct stuff no longer work anymore. I'd advise updating your save files at least every 3 releases if you want to ensure that they will always be usable
