While I agree with tank that most of the time there is little point chasing a heavily damaged or rtb bomber, most of the time you have no idea if its a second run.
I have let bombers go in the past only to see them re-run.
Its not as simple as you think.
You miss my point: It takes the 410 almost 12 minutes to reach 20k when light, and with the same firepower as an A8. The "exit the sector" comment was just to give a feel for how unimpressive that is. For comparison, the K4 can make 10k in around 2.1 minutes, 20K in under 5 minutes, and 30K in less than 9.
Just stop and think about that for a second.... Even at greater than twice the rate of climb of the 410, the K4 will still be hard-pressed to intercept and shoot down a set of B-24's at 20K without making stupid dead-six attacks.... assuming he upped the instant he saw the base flash.
Double that time, and the B-24s have already made their second pass if they're good. And by reaching 20K, you've already used up all your WEP, and so are even slower than your max numbers would suggest. Accelerating will be an issue, since you've climbed at around 170mph the entire time, and the bombers are doing roughly 287mph. Now he's turned for his third and final pass, and is lined up on targets.....
See what I mean? The 410 simply cannot intercept and engage typical bombers at even med-high alt, under anything but the absolute best of circumstances. If you want to say "Well, it
might happen..." fine, but the Help & Training section isn't a great place for long-odds.