"Would I gain anything by dumping the compressor?"
It would help get any further 'trash' out of the system.

"Did you use a variable orifice on your cars?"
I used the original and only changed the reciever/dryer.
The Volvo condensor is a pretty efficient one to start with, so it redily transfers the heat from the system to the outside air. High side line pressure is well within range. An expansion valve is almost always going to be a plus over an oriface tube.

Long story short. If too much heat remains in the refrigerant AFTER it's already been through the condensor, 'line pressure' will go up. When line pressure (high side pressure) goes up, the pressure held on the compressor (head pressure) is up. Eventual failure.

OK, that's what can happen with any system and what often happens with an R134a retrofit. On your car, the design is so that it's not nearly the concern of most older cars. In short, the factory system (PLUS a R/D swap) is well @ home with R134a.

Frank