Car is 4 years old and have not changed batteries in either of the key remotes. How long should they last ? Was thinking a little pre-emptive battery replacement might be a good idea.

 

Good question. I should probably be thinking the same thing. Especially with SmartTOP I hold the button down more than normal.

 

they are cheap and user replaceable CR 2032s, so thats at least a blessing. The BMW keys last years, but are not necessarily easy to replace.

 

So far, 5 and a half years on a Mercedes key, and four years with a Porsche key (the same keys in use all the time, I do not change back and forth). I just replaced the batteries in the Mercedes key, and as IslandS62 says, they cost about $8 and you can replace them in about 5 minutes.

 

I just replaced the battery after ~ 4 years, I found the operating distance had decreased. The batteries are a common type and I just followed the instructions in the manual. Very easy.

 

6 years here and it works fine

 

50 cents a pop i change mine evey few months cheapest thing i ever spent on the car

 

FOB batteries may last a very long time. I've seen batteries lasting more than 10 years.

 

OK. So the general feeling is that the batteries will last somewhere between a few months and 10 years . Guess I'll spilt the difference and replace the batteries next year when the car is 5 years old. Besides what are the chances of the batteries in both keys going on the same day ?