I usually let mine sit for a week or two unplugged, then plug in for a week and let it charge/desulfate, etc. I have twin 6V with an upgraded smart charger that treats the batteries very well. I wouldn't hesitate to leave mine plugged in all the time if I had to. In the winter, the batteries come off the trailer and get maintained by a Battery Tender.
2013 F-150 EcoBoost MaxTow
2013 Jay Flight 28BHS Elite
"My wheel lugs require more torque than your Honda makes!"