Ukrainians will only take so much. The Russian mercenaries were denied local support during the Donetsk airport fiasco. While it may take time for the new national government to get it’s ducks in a row, it will happen. If they were smart, they’d buy the mercenaries off and send them back into Russia with their weapons. Putin apparently never learned the lesson inflicted on us when we armed the Afghans. Now he’s arming Chechens. That’s guaranteed to bite him in the ass.
It's the same lesson we failed to learn from arming the Chinese and the Russians during WWII. They repaid us by arming the DPRK and DRV (as well as by direct military intervention), which inflicted 100,000 deaths on us during the Korean and Vietnam Wars. Ultimately, it made sense to arm the Russians to kill Germans and the Chinese to kill Japanese, hastening the end of WWII, just as it made sense to arm the Afghan mujahideen to kill Russians, hastening the end of the Cold War.