I would do it simpler than that.....on odd number days, set it to
#1, and keep it there. On even number days, set it to #2 and leave it there the whole trip. if you run the battery low, you have a backup battery to switch to if you need it. Want to make sure you are exercising both batteries so they last longer.
assuming you don't have an extremely powerful radio setup or a ton of electronics, and spend a decent amount of time underway, boat should be able to re-charge whichever battery you are running on that day and end up with two batteries fully charged.
a more elegant solution is the blue seas with with ACR which is a dual circuit setup (start and house battery), and simple On and OFF switch. Either way works but always good if you understand the How.
I ended up switchign from a 1/2/both/off switch to the blue seas dual circuit with ACR mostly because I was catching voltage sags when switching through the "off" position and it was frying my connext screen.