As long as your charger has the proper "float" voltage, your batteries are better off staying continually connected to it. Trojan calls for a float voltage of 13.2v. Every other battery manufacturer I have checked on called for a range of about 1/2 volt (e.g. 13.2v-13.8v) for float on similar batteries. I suggest you hook your batteries to your trailer, leave the charger on for a few days to be certain you reach float mode, and then test the voltage AT THE BATTERY. If it is 13.2 (13.2v to 13.6v would be fine IMHO), then your charger is perfect for long term storage. If your float voltage is outside of that range, then you may be better off disconnecting your batteries for storage.
The other normal maintenance is checking your water level. How often you need water will depend on how you use your batteries. Batteries will lose water when boiling. Boiling will normally occur when recharging a deeply discharged battery. The more often you discharge your batteries deeply, the more often you should check the water level.
I've read that if you live in a very cold climate, you should remove batteries for the winter. I'm not too sure about the details, as my climate is moderate.
'04 GMC Sierra 2500HD, CCSB, D/A, MaxBrake, B&W Companion, Retrax Pro, AR Power Steps
2013 Rockwood 8289WS w/Diamond pkg
1969 Camaro RS/SS Convertible
Dad's old 1968 Empi Imp (recently recovered from under 21 years worth of boxes/dust)