What aux batteries have you had the best luck with?

We have two T-105 Trojan 6-volt batteries in series in our 2004 Tioga, still going strong with some abuse/neglect. Check around for best price, try golf cart service shops. Wide range of prices. Looks like they're selling for around $138 apiece around here. Turn in your old batteries for rebate.

A lot depends on how you use it. If you go camping and use some of your battery, then move on and charge when driving, I would buy the longest warranty car battery. You should get 8 to 10 years from it.

But if you use all your battery occasionally, you want deep discharge batteries that can stand that and come back when you recharge. More expensive for sure, but very seldom really needed.