Can I farm XP/resources on a VIP extraction mission?

I've just been tasked to recover a VIP from a hostile area by the council. After the VIP has been found, I have to get her to the extraction zone. During this time, aliens spawn randomly on the map.

Right now I way outclass the aliens that are appearing - they're Thin Men and I can typically one-shot them. Additionally, if I leave my team in overwatch, the aliens typically drop into areas with no cover and stay there through my turn. Suffice it to say they're sitting ducks.

It occurs to me that I could just farm these guys - both for XP and for weapon fragments. Is this actually possible? Will I continue to get credit for kills while I'm in the progress of extracting the VIP? Is there some failure condition I will eventually run into? Or do the aliens eventually start to get harder, which would limit my gains?

Solution 1:

The aliens in extraction missions spawn neither indefinitely nor randomly. Spawning of each one is triggered when the VIP reaches a map area.

After you extracted the VIP, you still need to take out the remaining aliens. So you have to kill them all anyway.