Try to never start the engine after disconnecting from shore, genset off, when your panel had been reading "Bulk" charge. I like to have been well into the "Absorb" cycle before unhooking and cranking the engine, preferrably down to 14 volts or less on the panel. Our alternators, though heavy duty, were not designed for bulk charging house batteries back from deep cycling over the length of time necessary, on top of their regular duty task of engine and chassis device operation. They can and will overheat and burn rotor insulation, connections, circuit boards, etc. - as Steve says, they'll fry. No cheap replacements out there. Remember that whenever you've been dry-camping.
In a hurry to break dry camp? Start the genset several minutes before the engine and let it charge the deep cycles for awhile as you drive, taking that load off your alternator.
Joel