this is pretty much the argument for a 30s repair delay 
You really think that an enemy should sit still long enough for me to pump 4-5 more rounds into him? Really, about 8 seconds is all I need. 5-6 for the reload, another 2-3 for flight time, and hes either dead or disabled again with a damaged engine.
Let me put it this way; if after having scored a hit that damaged the enemy's tracks, you're unable to score another hit with the next 2-3 rounds, then he kinda deserves to escape.
enough time should elapse so that any tank can get at least 1-2 more round off.
Like I said, 10-15 seconds.
Maybe 20 at the outside. But I think a lot of people wishing for this aren't aware how long 30 seconds can feel in a GV fight. Go out there, and next time you get tracked or damaged, wait 30 seconds before clicking on that resuply button. Come back and tell me if you think 10-15 seconds would be better.