Generator Surging/Dying After Hours of Operation

sea foam is good stuff
BUT it wont fix a bad float in the carb
or a weak fuel pump
or a bad /clogged pickup tube in the RV fuel tank
what was the fuel level during the 'problem times'
and have you tried running the generator with the gas cap loose
a bad vented cap that is clogged can cause problems with the generator that you might see with the drive engine becuase of the difference in fuel systems