I'm happy with that. We have many battery banks operating fine at 40 to 50 degrees F also. You just have to compensate for the reduced amp hour storage capacity by buying more amp hours of battery than you would for a 65 degree battery temperature. Lead acid batteries will last longer if they are cycled less deeply. I have seen, twice now, in my fourteen years of working with these batteries a cell that would not take a charge no matter what I did.
Manufacturing defects do happen and they show up very early on.
So check with the hydrometer for bad cells. This offer is good for one year after purchase with Trojan batteries. Surrette batteries carry a longer warranty. If you really want to get the most out of your battery investment then by all means rotate. To rotate the individual cells, or batteries, simply disconnect them and move them to the middle of the bank once per year.