During the course of resolving a false positive I just reported, I found that all of my file exclusions have been lost. I’m on the latest version of Avast! 8 Free (8.0.1483). They were there when I setup Avast! - the version that was current at the time of my first post (last year sometime).
The exclusions from v7 (affecting on-demand scans only) were replaced by Global exclusions (affecting shields as well) - so yes, those are lost during v7 → v8 update.