I have these same bags and tow a 6,000lb, 29' trailer. They make a huge difference. I also decided to go all out and get the WirelessAIR on board air compressor system. The push of a button on the wireless remote and the bags inflate to 35 PSI. Push another button and they deflate to 10 PSI. It also monitors how much air is in each bag and will automatically add air on it's own. I still added the valves for manual inflation/deflation for each bag in the event that the wireless system fails. This was an expensive way to go but it has a huge coolness factor at the campgrounds.

 

Have gone through two sets of air bags, don't think any of them like the cold temps of Manitoba in the winter, keep on splitting apart with 5-10 lbs of air in them. Finally said screw it and haven't replaced them.

 

plastic in the real cold
did you contact the people you bought them from about the cold temps

 

I bought these when I lived in NJ...installed before the dead winter hit...no problem all winter long. In the summer of 2012 I moved to FL and had them since no leaks and still going on strong (knock on wood). I set them at 10psi for normal driving and I've gone 2 months and never touched them. When I tow my dads boat, 25' CC Mako apps weight 6800lbs no problems with sag and works well pumped up around 25psi.