I used VHT about 8-9 years ago and it still looks brand new. From what I found, heat is the most important aspect to the paint working as intended and getting an even finish.

I painted mine in the basement during Winter. The temp in the basement was around 55 but, I had two heaters pointing directly at the air cleaner. I think I would have had better results with even heat; like the temp in the room being 80 or doing it out in the sun, etc.