I decided to try the fancy new tire pressure monitoring system when we got the bus. It works well and I think I like the piece of mind. I guess if I had an inside tire with a nail it it, I would know sooner. Thats a good thing. I hated always watching our tow car when we had the Allegro bus. A TPMS on those tires would have been a wonderful thing!
Since we don't tow now I got the cheap one because it was the only one that just monitors 6 tires. The monitor that sits on the dash is solar charged. I closed the shades not thinking and 2 months later the monitor was dead. After charging it I had no tire pressure readings. Luckily I had the monitor in my back pocket getting ready to throw it away when I unscrewed one of the sending units from a valve stem. As soon as I did that, the monitor came to life with a "beep" and said zero air in that tire. I screwed the sending unit back on and got tire pressure reading right away. I unscrewed all of them and put them back on, and aaaaaaall better. I guess it just had to re sync.
Hope that helps somebody else.