Currently, most of my relatively small/middle models can take up to 3 hours to upgrade, and that with a new fast PC.
Moreover, I receive many errors, starting with the "there is a circular chain..." that only gives the option to delete...really? DELETE part of a project model to be able to use a newer version of the software? And no even knowing what you deleted because the ID of course no longer exists when is finally opened.
Also, once upgraded, the model is a bit modified, for example the 3D cutbacks adjusted with "Change Reference" (see other Idea: https://forums.autodesk.com/t5/revit-ideas/framing-3d-cutback-default-options/idi-p/7891288) were reset back, so I have to redo everything.
I understand the philosophy behind the upgrade and compatibility (I think) but, if this is something that we have to do, for every single model, every year, it would be a huge help if this could be faster and cleaner.