The first set of sensors I had for our TST were the original ones and most of those lasted over 6 years, with 2 having to be replaced just before the 6 years. they are on the coach all the time. They are not difficult to remove and add air to. I am on the second set of sensors and now and in the 2nd year with no troubles. They have a trade in program for less expensive replacement. It is a good system for most people. If I were to replace the whole system, I might go to the 507 with the replaceable batteries, but am happy with the one we have also. Hope this may help. Happy Trails Bert
