i was wondering, tpms sensors are battery operated, what is the life span of the sensors and when should we be replaceing them....

hard to tell how long theyll last. just wait till you get a tire pressure light on and the pressures are ok. youll have to have a tool that will read the inputs from the sensors to determine which is at fault.
ive found more are broken than actually go bad... from improper removal/installation of tires

yeah ive run into one so far, it was on a caravan. but ive had some problems on some honda where i have to put more air in to the wheel the make the light go out...

might wanna check for a leak then...