Perhaps I did not state this clearly.
Roughly 2% system fluid capacity loss.

I have a 55 gallon vacuum tank pulled down to 30 inches mercury, with a high capacity two cylinder 220V 50 amp 20 hp commercial vacuum pump, recovering to a 30 pound high pressure cylinder.
I can suck a car or truck system dry in seconds.
Pulling the charge that fast also sucks most of the free oil out of the system = 98%...
The O rings I get in 1000 unit selector boxes.

On two of my cars I did not change the O rings because they where going to part out in less than a year.

I will not replace the R12 compressor shaft seal until it begins leaking R134A, in many cases it is cheaper to replace the compressor when it fails.

I use 32 ounces of Acetone while flushing the average system, and that stuff is dangerous to work with.