You're right, it would depend on the heat of the kitchen or where the kefir is being fermented. We keep our house between 68-70 year round, but I suppose our kitchen would 'heat up' when using the oven and such. The kefir is sitting right on the kitchen counter.
My grains haven't really grown that I've noticed, at least not a lot. I don't rinse them between batches so it's hard to tell. I just made another batch this morning and it seems to be a heaping tablespoon of 'grains'. I don't necessarily want them to increase as I'm getting way more than enough milk kefir as it is!
I keep thinking I should let them rest and just feed them in the frig for awhile, too, as I'm having a hard timing keeping up with drinking so much of it! HA