Of course it won't die till one of us steps away. Its not like we have anything but speculation to go on in these hypothetical arguments. That means its your oppinion against mine.
1: most of the people you want to keep from getting to the fight (ronder, snarglie, Dr7, myself, 0nline, etc.) will be following the action (not where you want to set up). That means your ambush has accomplished killing the cannon fodder a few times each.
2: you seem to be under the impression that a furball going on overhead means that everyone not fighting will be killed in a few seconds. An La-7 on the deck can be damn hard to catch. You also seem to think that the furballers will head to the other side of the base to kill a spotter. But I do admit that I hadn't concidered this with an airfield in mind; I was thinking about them being used to defend V bases (if you set up on the field, you can be damn hard to shift).
3: so you plan on spending your entire time in one spot? Once a few guy get killed, people will stear clear of you. I'm still amazed at how fast some people can figure out your field of fire.
4: so you want to be left with however many shells the gun crew can carry in their arms? If we do get this, the ammo will be left where the M3 put the gun down, or it will stay in the M3. In the case of the former, your ammo will be as targeted as supply boxes. Whenever I see some supps, I use them up, or put a shell on them.