fwiw I also observed a persisting slowdown soon after upgrading my Studio to OSX 26. Since I haven't been using it very much I'm short on data bearing on the cause -- maybe it was GPU use though I don't recall doing anything like that.
My Intel Mac from 2015 could be up for months without interruption or slowdown. (mostly because I stopped updating after Mojave, but my point is it never needed a reboot)