I wrote the reply below in another forum and figured some of you might be interested in it...FWIW This was in reply to a post in a thread entitled "Things that annoy you."
Gregor, post: 11702443, member: 17524 said:TPMS. The only time it ever kicks on is when we have a very cold snap. So I'm on my hands and knees at some gas station airing up the tires.
A couple of problems with TPMS and their stems...
There are two types of stems. One is a regular-looking, rubber "snap-in" stem which work great. Then you have the silver metal "can" type...these are more prone to leakage. With the rubber snap-in style stem the entire outside of the stem is rubber which creates a thick rubber seal at the valve stem hole. If you bump this stem...washing the car, a tree branch is run over and flips up to strike the stem, etc., the rubber stem has the ability to flex a great deal. With the metal "can" type of stem they are rigid and made of a type of aluminum(?) that is subject to corrosion. There is a a small o-ring inside these metal stem assemblies. As the stem ages a spot of corrosion can cause that little o-ring to start leaking. Being of a rigid design, bumping the stem can definitely cause the stem to leak, not always but it certainly increases the chance. I've seen the metal stems so corroded that to remove them you literally have to twist them in half or even reach for a dremel. Leaks from the metal can stems can be very slow...kid's soap bubble solution is good for detecting this...cover the entire stem with the solution from base to top (remove the cap)...and give it time to create a small foamy area which denotes a leak. If the leak is very bad it won't take long to tell you, if it's very slow it can take a few minutes.
When the sensors get older their batteries start going out and can be aggravating for the car owner. If your TPMS light comes on and all of your tires check out to be properly inflated be sure to check your spare tire...sometimes they include a sensor but are almost never checked. While we're on the spare...when was the last time you checked the air pressure in yours? Sensors have come down in price over the last few years but still cost a fair amount. A large tire dealer or car dealer should be able to test your sensors and replace them.
TPMS systems have a "set point" of several psi. You should still regularly check the psi in your tires. Some systems have as much as 5psi of a set point...a vehicle spec'd out at 35psi won't alert the driver until the tire is down to 30psi. Or, a setpoint of 3psi wouldn't alert the driver until a tire got down to 32psi. The problem is most air loss is a gradual process so the tires could be under inflated for months before the TPMS light comes on at the set point. This means you are actually running the tires in an under-inflated/over-loaded state which affects safety, handling/performance, carrying capacity, tire wear, gas mileage, etc.,. So, regularly checking your tires' psi will pay dividends. Look for your specified air pressure on a label attached (usually) to the driver's door post or running board. I wouldn't object to having an extra couple of pounds of air in my tires.
Winding up here (this got much longer than I intended!). For the first few years after TPMS came out the systems were thoroughly aggravating and they still are to a degree. But, what they will do is save you from having to buy a tire that on common vehicles are $125+ dollars on up to literally several hundred dollars. As you're driving down the road and the light comes on you have an opportunity to pull over and check your tires before you get to a "run flat" condition in which the tire is totally destroyed. A leaking tire can often be repaired if not run-flat. Even more important than keeping from destroying a tire, a TPMS alert also prevents you from experiencing a catastrophic tire failure at highway speeds, which can be deadly, seriously.
Tires will lose air pressure naturally over an extended period of time...nitrogen filled tires help slow this process down, but even those tires will gradually lose pressure. If you wait until your TPMS light comes on you've waited too long to check the air pressure in your tires *or* you're experiencing a leak of some sort. If you regularly (once a month is best) check the air pressure then you will get the best tire wear/mileage, best gas mileage, best handling and performance *and* you'll know when a TPMS light comes on that you have a real issue.
As the OP mentioned, cold weather can drop your tire's air pressure by several pounds. I mentioned that I don't mind a couple of extra pounds of air in my tires...in cold weather I especially like that little bit of extra air. If you do add a little extra be sure to check out the ride and handling of the vehicle as compared to where the air pressure was before as it may (or may not) be different.
One last minor tip. Keep valve caps on your valve stems. The caps keep moisture and dirt from entering the valve and causing problems. Walk up and down the street and see some nice vehicles with the tires' valve cores exposed to the elements. Cheap insurance.
TPMS is aggravating/annoying. But if the driver keeps a check on his/her tires' air pressure and pays attention to the TPMS alerts then money can be saved...and possibly even lives.
FWIW
Naturally our Honda Pilot has the metal stems and my 2003 jeep has no TPMS. 
