When you park that trailer, you need to disconnet the battries otherwise they will fully drain in the months it is parked. This will cause the batteries to crap out.
I make sure my batteries are up to full charge when I park and pull the connections. About every 3-4 monthes I will trickle charge the batteries to full charge and disconnect again. Doing this I get about 3-4 years on the batteries before replacing. I also use deep cycle marine batteries.
I learned this the hard way when I fail to disconnect the wires to the terminals and I had to replace two batteries within a years time.
RELH