When plugged into shore power my battery gauge shows full charge because it is reading the charger voltage.
The sneak circuits in my TT will drain the battery in about four day when unplugged.
Between trips I keep the TT plugged in and check the water level in the battery. My battery charger switches to trickle charges automatically, Some do not so it is best to keep an eye on the battery water.
My battery disconnect switch is a 1/2" end wrench. Simple, effective and not likely to fail. I disconnect the negative lead and tuck it into the battery case.
Have fun.