Just to jump in ( no harm intended )but I think some one is feeding you a line of BS, that many miles a day 7 days a week, Should more then enough to keep it up, After all how much could the system draw unless very bad designing, what is alt supposed to put out ?,,,,,,,,,,,I would hope at least 30 amps in todays world about 60a is the least ive seen even , That has a great residual in 30 min run time, There must be a draw some where, Some one is not catching ,Even in the old days with mechanical clocks and stuff like that you could let the old boats set fore a couple a weeks with out problem ,Just my opinion ( no harm intended )