Its a bit late to help you as I see the A team are on the way... I have changed the batteries several times in our fobs for our keyless entry XC90, they seem to last about 2 years of hard use.. they have never needed a re program after battery changes. I thought but cant be sure that the main dealer should change these in one of the service intervals?, at least the fob that comes in with the car?? May be worth checking.. We now use an independant Volvo dealer to service our car as the local main dealer was not good.. hence why I change the batteries myself. I also change the battery in the spare fob ( although not at the same time ) so I know the battery levels are good.
Good luck MM I hope all goes well for you..
dave
