1999 Chrysler Town and Country A/C Failure

I have owned this mini van since 75000 miles. When I bought it I noticed it had a reman compressor. It wasn't too long before that died. I replaced it with a new compressor. Being cheap, I flushed out the system, and did not replace the condenser. I did replace the drier, the o-rings, and the expansion valve. I evacuated the system, and enjoyed the cool. However I did not find the leak, and after some time, I had to add refrigerant on a monthly basis. I never could see a leak using UV Dye. My question is where are these vans prone to leaking? Should I have changed the evaporator? Does this entail complete removal of the dash? Where is the back evap? Does it usually leak? I have just purchased another round of parts, and am ready to sacrifice another weekend, but I really do not want to do this again. This time I have bought the following:
NEW COMPRESSOR
NEW CONDENSER MAIN
NEW CONDENSER SUPPLIMENTAL (REAR AIR)
SUCTION HOSE
DISCHARGE HOSE
DRIER
EXPANSION VALVE
EVAPORATOR FRONT
NEW O-RINGS
Is it likely that I should do the rear evap and expansion valve too?
What could a repair like this possibly cost at a shop?
I had to take the whole front of the van apart to do this the first time.
Thanks for any advice that you can offer.
AL