How long can you go on a 50 amp extension cord?

I’m currently running one AC on a 100’ long #10 cord plugged into a 15A outlet. I routinely run 2 15K ACs on a 30A outlet...what the OP is wanting to do using a 50A cord. Each AC (15A) SHOULD be on its own leg of the 240V/50A ...even if both AC are on the same leg (easy enough to correct) it’s not going to be a problem. Another thing that only in the RV world do we worry about ...16A on a 50A wire.