I'm not sure that it takes a complete recharge to get the level right in a 210. They have the infamous warm left vent if you're just a bit low, so you know. You can also watch the high-side pressure when it's hot outside to see if you have too much. That said, it does take complete knowledge of the system to wing it this way.

Note that even with a complete evacuation and recharge, you still have no idea how much oil is in the system. That is, unless you flush everything out and drain the compressor.