Wiki says that some american WEPs used water-injection or water-methanol systems, so the water tanks must go empty after some time...
I ran a P-38L at 100% power, 100% propeller for an unlimited time. But with a P-51D, after running at WEP, 100% propeller, the overheating message popped up and moved the power down to 100%. The overheating message didn't disappear and after a while the engine died.
