I've dispatched with a failed alternator in a piston twin.
The other failed on the return sector and the battery was shagged as I arrived at destination.
Lesson? Never again.
So have I - VFR only!
What happens if the other one fails (?) - same as a SE with only one alternator. Shut as much electrics down as you can, lower the gear and truck on to your destination or alternative - using your portable VHF, GPS, cell phone as necessary.
Hardly a big deal!
Dr 