I did some experiments a while back with annealing PLA in a water bath (using a sous vide device from my kitchen). I made 4 test pieces and held 3 of them for 60 minutes at 70C, 80C, and 90C. Then I put all four pieces in a 210F oven with 85g tungsten weights on them. The unannealed piece deformed and the weight fell off after less than 10 minutes. The rest were pretty much stable for the next hour.
I used this technique to then anneal a garage door opener holder (printed in the same red PLA) for my car, which has survived for 1.5 years with 2 summers of hot sun parking.