I know with my ACR PLB it was actually cheaper to get a new one than to change the battery...
New smaller/lighter PLB goes into my survival suit since I fish on the Bering Sea, old PLB goes into the truck.
Pretty sure I've got the ResqLink Plus in my survival suit; ACR was running a killer promotion last December. Came with an (un-expectedlely) high quality survival/first aid kit!
Honestly, I'd feel much much better about getting any kind of lifesaving equipment new and unused. But that's just me.