I leave games if I see that we have absolutely no other choice, even if I have a 2nd base, if I see my partner has like no guys, and I'm trying to pump them out, I give up, I can't take them myself....
I never uproot, uprooting is worthless, I might as well leave anyways. The army isn't going to decrease once they leave my base, they're going to go to the next one and probably rhomp on them too... and it will be the same situation over again, only this time it will be 2v3 because I won't have a base to really help, I only establish an expansion to get gold or wood, not to produce units from..