Is there any reason to upgrade from version 6.3.3 if I don't do MU [considering retirement in 6-12 months]?
Only if you like change. The best thing about V7 is the direct updox limk, along with being MU certified (which is not a big deal for you.)
Stick with 6.3.3. The others seem to be stable, but not a lot of interface changes, mostly background things and fixing bugs. Other changes are MU stuff
