Some experience to add to this thread:
3-4 months ago I* installed a dual battery system (Columbia Overland tray and National Luna kit) into my 05 V6 Tacoma. I put in 2 group 35 Autozone Duralast Gold Batteries. I had a good reason for using 2 starter batteries rather than 1 starter and 1 deep cycle... But for the life of me, I can't remember what that reason was.
So, anyway, on Saturday I went to start the truck and found the starter battery to be 100% discharged. I put it on a trickle charger for the whole day and it still wouldn't hold a charge. Drove to Autozone this AM (the jump-start feature on the dual battery system works great!) and they tested the starter battery to find that it was, indeed, quite dead.
I find it rather disconcerting that this happened. The battery was practically brand new and had never been abused in anyway. It has never been below 12 volts in it's entire life as far as I know.
At any rate, I got the full refund on it... And applied it to an upgrade to an Optima Yellow Top. So, I now have my old auxillary battery (Duralast Gold) in the starting battery position and an Optima Yellow top in the aux battery position.
I'll update in a few months or years when I know how that system works out. Hopefully it was just a fluke bad battery. If the 2nd Duralast Gold fails, then I'll swear off them for life.
*I installed the dual battery system... With a lot of help from Marco.