Once you get good at shooting, the ammo lasts longer. Buff guns have convergance set at 500meters, so if the enemy is off that zone you can save ammo by shooting only one position rather than all (check keyboard settings).
Most players feel the fighter/bomber equation is slanted toward the bombers, because the gunner has 20-30 50cal weapons at his command with little accuracy penalty for wobble, etc. Also, most AH2 attackers conveniently come up the 6 -- making kills easy. Some guys are scary good at the attack profiles, tho...
"Endless upping" happens because solo 30k bomb runs are "endless flying." Interceptors' climb rates are accurate, like it or not -- and the G10 is not a perk plane. If you dont like getting killed by the same guy, get good at killing HIM. I've no bomber ace, and I've killed the same guy twice on a run.