From what i read, and what mechanics that i know i can trust told me, the 1999-2001 Durango's were horrible with this problem. If you got a good one and it didn't break in a few years or the evaporator didn't leak you were alright, but otherwise its a job that takes a full day or more to replace the evaporator, saw one being torn apart for it, WOW, they had the whole dash out on the shop floor, even the steering column was loosened and the steering wheel removed to give clearance to remove the dash.
What i was told is if you have one of these model years and your evaporator needs replacing to make sure you get a new one not a reman, or make sure you get one from a 2002 model year in the junk yard, supposedly they redesigned it slightly starting in 2002.
Oh, and not to stay off topic here but this does technically relate to any vehicle, however if you have a Durango though make damn sure your evap drain is clear and not building water in the bottom of the airbox as i helps speed up the failure rate.
I surfed through websites and forums before buying the KJ, and after reading stuff here and stuff on Durango forums i finally settled on buying a KJ.