[twindman]

I have the 507s. Probably 7-8 years old. I got a new monitor and the repeater as my right rear also dropped every couple of days (or weeks!). I think I have changed batteries once on all of them and a 2nd time on one, but I am not sure it needed it.
FYI One thing on the old ones, when you pull in somewhere and someone else in the area has the new ones running, I will get things like 500 PSI or such. I researched and called TST and they said the old monitor has trouble with the new ones and reports strange readings. It is no big deal now that I know about it.. Only happens when others are close by like campsites, etc. I think maybe it happened once at a rest stop too.