Anyone else seeing M365 apps requesting frequent authentication? Not so much a problem, but an annoyance as many users have to do a full MFA authentication after only two hours of using Excel for example.

This sounds like an issue with SSO for non-persistent VDI. You'll need to determine if you're using Seamless SSO or Hybrid Joined Instant clones, and go from there. Usually this occurs when using Hybrid Domain joined Instant Clones, and not having the conditional access policies configured to handle the MFA requirement. If you're using Seamless SSO, it may not be functioning, and SSO authentication may be failing.

i have this exact thing with just 1 user, started about 3 weeks ago randomly. she has to re-auth after 2-3 hours. we use pooled vdi vm's with office2021 ltsc tho. its really odd its just 1 user out of 50....i did give her a new windows profile tho and it fixed the issue