Since you said Walmart, I have to ask..what type/kind of battery?
Most dry campers, at least on here, don't use WM batteries.
Nothing wrong with Wal-Mart batteries ;)
I have 4 each group 24 WM batteries in my boat (2 from 2011 and 2 from 2012). 2 of them are deep cycle and 2 of them are dual purpose. Also have 2 each deep cycle group 24 WM batteries in my TT. I've had ZERO trouble with any of them.
A WM battery is no different than any other battery on the market: maintenance required! I put a trickle charger on my batteries at least once a month, regardless of their charge level. I trickle charge my trolling motor batteries after every use.
Regarding how long they can last, its hard to answer that one. However, I know I can run a bait well pump in my boat all day and night with no problem. That sucks way more juice than a few lights ;)