When you say long voyages, just what do you have in mind?
Yes, you can load up on batteries to run electrical appliances , but again, just what do you have in mind? A computer or small TV or do you want to run a electric hot plate or air conditioner?
We need a lot more details.
how do you plan on going to the bathroom? You going to have to take a port-o-potti to shore every couple of days to empty it.