The evaporator on my 09 Enclave went with only 13,000 miles on the odometer. Then my HVAC case was warped and had to be replaced. I even had the thermo expansion valve problem, as well as an AC tube leaking. All in all, the AC has been the most troublesome in my 09 Enclave, requiring the dashboard to be taken out twice. It was covered under warranty, but a major hassle. When they replace your AC evaporator, I would also have them replace the HVAC case at the same time - there's a TSB on the warped HVAC (according to my dealer; I don't have the number). When I did research on the HVAC case, I saw several different part numbers for the 2008, 2009, and 2010s, indicating a possible problem/redesign. (This was for the automatic tri-zone AC case).