Luckily our car went in for a service yesterday and they couldn't re-sync the keys at all.
In the end, they had to replace the unit as it has water in it. Now say it won't (shouldn't) happen again.
It's bad enough having to always go to the driver's door to unlock/lock the car, but the fact that the key wouldn't switch off the alarm until it was in the ignition was a right PITA.
It was such a chore as my daughter's car seat is in the opposite corner to the driver door, so whenever she was in the car it meant getting her to come round to my side of the car to wait in safety, unlocking it, having the alarm go off, sticking the keys in the ignition, taking her around to the opposite side, putting her in, then going round to the driver's side again to get in.
And as for getting her out it was equally problematic. No wonder we were all so much fitter in the old days.