We leave our dual Interstate 6 volt batteries plugged into shorepower year round when stored in our backyard and our Iota does a great job keeping them fully charged.
The Powermax Boondocker will be a huge improvement over the WFCO, your Trojan batteries will definitely be happier with the changeout. We don't use our battery cut-off switch as it would not allow our Iota to charge our battery bank if implemented.
We routinely check battery bank fluid levels, ensure connections are tight and corrosion free, and normally top-off once a year as there is very little fluid loss even when hooked up during summer months. We have 4 years thus far on our Interstate GC batteries from SamsClub and they are performing well.