I guess it depends on how long you're planning to keep the car. A friend had them start failing on his Toyota starting when it was about eight years old. They turn when the car starts moving. So, it's operating hours that determine their life.
I'm an obsessive record keeper. I record and reset my on-board computer's average speed when I fill up my gas tanks. From that, I can calculate the total engine run time on my BMW's. I first wondered what use such data would be. But, if I ever have a TPMS sensor fail I'll have a good idea how many operating hour it took.
I'm getting tires this year on my almost six year old 535i. I'm debating taking the risk not changing the sensors. I plan to replace the car when it's about nine years old. If I win that bet, I've saved ~$400 on new sensors. If I lose that bet, I'll have to pay for them removing and reinstalling the tires an extra time (~$150) if the sensors do go bad. So, I have to ask myself. "Do you feel lucky? ***8230; Well, do ya', punk?"
I have six people waiting for my 535i when I'm done with it. I could try to add part of the cost of new TPMS sensors to the price when I sell it. That'd be a bargain for the next owner if they're only keeping the 100k+ mile car a few years.
Only the U.S. spec' F10's came with TPMS as standard equipment. The rest of the planet got FTM (flat tire monitor), which uses the ABS wheel speed sensors to detect a tire that is going flat. But, FTM only gives an alarm when the tires are about 25% under inflated. Ralph Nader's group took the US DOT to court and demanded that they make the more sensitive TPMS required on US cars. So, anybody keeping a car around ten years gets hit with the $500+ Ralph Nader tax.
