I can add just more confusion to the question. I have valve extenders and a TPMS on my 34' motorhome. I have use the extenders for the entire 7 years I've owned the coach, with no issues. However, I did have a couple of sensors on my TPMS start leaking, but I replaced them. I am just getting ready to contemplate new tires. Mine are 7 years old. When I met with my tire guy, whom I trust implicitly, he said "when we replace the tires we will put in long stems to get rid of the extenders. You really don't want to use extenders, they leak all the time." So I got the same answer from my tire guy, yet my experience (and others who have posted here), seems to be the opposite. I'm interested to see if anyone chimes in with stories of leaking extenders?
Steve