On a whim, I purchased a clementine mandarin for my BF, thinking I would only need to bring it in when the temps drop below 20F, which doesn't happen very often here. A little research has disabused me of that notion; looks like 28F or so is the magic number. It's one thing to bring a tree in a few times a winter, it's another to be hauling it back and forth for months. Nor, I suspect, is repeatedly jolting the tree from cold outdoors to warm indoors good for it.
I am trying to determine if I have any suitable indoor winter spots. My house has deep overhangs, so I don't get much sun even in the winter at the south facing windows. 4 hours at best, and then only on the floor and wouldn't hit the top of the tree. The temperature indoors is 65-70F, even in the basement although that runs about 5 degrees cooler. The windows in the basement are small and get less sun, but could possibly hit the top of the tree. It is, however, fairly humid inside since I have gas heat.
The garage rarely dips below 45-50F but gets very little light and is of course prone to the occasional cold air blast. It does heat up on warm days.
My experience with citrus is limited to growing it outdoors in CA, and I don't recall that the trees ever go dormant. Can citrus trees be coaxed into hibernating for a couple of months -- i.e. in a cool garage?
I would give your basement a try, with an overhead shop light, with a bi weekly misting, in addition to watering, with the idea of just bringing it in every winter. You can prune them to a certain size so each year you aren't trying to bring in something that is getting bigger and bigger. It would eliminate the in and out, which in a hurry makes it not worth it the fuss, IMHO.