doing it one by one is very annoying. I have to log in to upload the latest package, reset,program and make a router upgrade.
Netinstall is not an option because new SXT by default starts from nand. Every 2 months I spend about 8 hours on programming sxt one by one.
is there more efficient way?

Have you tried Flashfig? At first boot, all RouterBOARD devices start in Flashfig mode.
http://wiki.mikrotik.com/wiki/Manual:Flashfig