If you need go in base, of course it is, but it does not affect rate of fire like someone is trying to prove. You don't use rocket arty just after cooldown has ended. You wait for a good target.
Same with AVRE you don't shoot right after shell is ready. Sometimes it can sit even fore over a minute before you pick a good target. Therefore going back to base won't affect your rate of fire, buecasue you don't shoot every 50secs.
I am certain that if you can reload sturmtiger on the move without any penelaties it will shoot alot more often.