Battery Shut off and Storage Question.

For the past 30 years or so I have simply disconnected the battery. If the battery was fully charged when I did so, it always had juice when I reconnected six months later. It may low, but still had enough juice to power everything. I'd just plug in shore power a couple days before leaving and all was fine. Why keep it plugged in if you don't need to? You are wasting electricity and unnecessarily using the electronics.