Have an 03 Monte SS (3.8). Bought it 9 years ago with approx 70k miles. Now has 193k miles, so I know the car pretty well. Have never had a car that goes through thermostats as this one does. Just replaced one. Needs thermostat almost every year. Always stick open, so motor runs cold and fuel mileage is reduced. Of course I only notice this in cold weather. Am not really looking for a "cure," but I would take one. Just seems like a puzzling anomaly. Haven't seen anything like this posted here, so must not be a common problem.

 

Where are you getting the product from? Might be the source.
I have a similar issue with light bulbs, depends where I get them for how long they last, some just burn out right after I put them in and I use a glove to do it. Crazy stuff.

 

Buying them all over the place. NAPA, AZone, GM. GM lasted best - 2+ years. AZ lasted worse. <1 year. Last one I bought (few days ago) is Stant from NAPA.

 

I had the same problem after radiator flush service, the shop uses to much pressure flushing and blows a hole in gasket. The good news is, thermostats are cheap and very easy to replace on this car, I use Stant premium $10, takes me 15minutes.