Whether you do or you don’t depends on your charger. Some are designed to be left on 24/7, some will hurt your battery. Do what the charger manufacturer recommends.
re 3 cell charger....good question that I can't answer for a couple of weeks. It came on the 1756 Lowe that I bought last year. It seems to work just fine.
That boat is in Texas, and I am in TN.
I am actually going to swap the TX boat for the TN boat in a couple of weeks. I'll know then! Ha Ha
rich