Agree with Al.
You didn't say if it was an internal or external regulator, but there are so many things it could be. Be sure an eliminate all the obvious ones first. Check all the connectors from the alternator and battery, loosen, clean and retighten.
But as Al pointed out the alternator could be on it's last legs. They can get flakey before they finally die. Looks like you're a single engine, so If you're going to be out of touch with civilization during the next 12 days on your trip, I would want to fix the problem before going on.