Do you update Blender as soon as a new version is released, or do you wait until you're done with the project you're working on? I'm hesitant to update to 2.81 right away because I am worried that it might ruin my old files. Once I opened a 2.79 file in 2.8 and it was ruined.
usually stay on the stable version when doing paid work. however i dl daily builds for personal stuff that i know are not that important. and keep them separated.
switching project from 2.79 to 2.8 can be problematic since they changed lot of things in the background. safest way i'd move is append the objects from the old 2.79 file to a fresh 2.8 file.
It depends on the need. I.e. if I work with caustics this 2.81 update might be useful, if I don't and my work will get nothing from it -- why would I switch? Don't really care about these numbers for the numbers sake. (Since 2.8)