I put once a year as I didn't do it for the first sixteen years of my battery bank, which consists of C/D forklift type batteries, 1860 ah. I knew we were supposed to be doing it but I didn't understand much about it til I began hanging around this forum and a couple others the past couple yr. Now I've begun doing it, though any damage I've caused is, by now, perhaps permanent. On the other hand, my batteries are now 17 yr. old, not as good as they were but still working ok for now. Meanwhile, my nearest neighbor, a mile up the road, is on his second set of a well-known "solar" battery set in seven years, and he paid more money for his and they are half the storage capacity of mine. The deal is, he is religious about checking and eq'ing his set and has a more modest elec. useage than I do in his cabin. I have a few other friends who have about the same experience he does, buying pricey "solar/pv" brands/models of batteries, messing with them all the time, and getting less [or far less] life from them than ten years. I don't know why this is, and why people don't buy forklift sets, or how much damage I've done to mine in the past, if any, but I have begun eq'ing mine now and plan to do it more often than once a year. Note that I am not promoting the idea of not equilizing, I simply was ignorant when it came to the technicalities of it until recently. Actually, I am still ignorant but learning, and we've been pv and off-grid since '85. Slow learner, yes. But for whatever reason, my batteries have been great with almost no work from me. I have the recombinant caps and thus have to add water once a year, at most. [For eq'ing, those caps must be removed or they'll overheat and melt, as I discovered the hard way.]