AC compressor / condenser replacement, round 2

AC went out in my 2011 Prius. Took it to Toyota hoping it just needed recharging. They said compressor is shot, need to replace it and condenser. $2800

I got a rebuilt compressor from a very reputable company, a new condenser, and took the car to a local mechanic. After he finished the job the AC was ice cold but then it quit again a few days later. I called the company that I got the compressor from and they said that it likely was caused by contamination, and that the evaporator should have been replaced as well. (Toyota stated only compressor and condenser) They sent me another compressor at no charge. He was pretty clear that if the evaporator was not changed or at least cleaned properly, it would just happen again. He also said my new condenser was now contaminated and it would need to be replaced as well. He said the condenser could be cleaned, but it requires special equipment and involves nitrogen. (No idea on this)

My mechanic disagrees with this. He is adamant that he cleaned everything the first time around, and he can just clean the condenser he just installed and that it will not need to be replaced. I know he didn't use the kit Toyota makes for cleaning the evaporator though so it likely wasn't clean enough. NutzAboutBolts has a video on it and it's very easy. He did say he would do that this time if I get the kit.

I am worried that this will just happen again. The company that I bought the compressor from, that is all they do is rebuilt compressors. He seemed to know this subject inside and out. They didn't need to send me another one since pretty clearly my mechanic left contamination somewhere in the system, but they did anyway. He said any contamination will kill the second compressor, and if a single drop of water is introduced into the system, it will kill it as well. Leaving that condenser in there even though it is "new" worries me a lot if there is any chance there is contamination in there that can kill a second compressor.

This is the one system I did not feel comfortable working on myself. Figures it would be the one that goes out. Any advice anyone has, greatly appreciated.