I have an Garmin Nuvi that's 2-3 years old. The battery no longer holds a charge well. It runs on the cord just fine. Would it be worth me buying a new windshield mount and keep using it?
Probably, because stand alone GPS will be obsolete in a couple years as smart phone tech gets more affordable. Get as much out of it as you can. For the price of a $20 mount you'll get quite a bit more use out of it.
You might be able to take the back off and take a look at the battery...many of them are replaceable.
what happens when the batteries start to die on your gps? does it give random directions or talk funny or something?
the voice gets replaced by Deicide, and screams instructions at you. MERGE RIIIIIIIGHT!!!!!!! Good electronics gone bad. =( Not a good way to start your day. And certainly not part of a well balanced breakfast.