How low is too low for cats?

[Koppur]

I have 2 cats and I turn my heat OFF during the day all winter long. And for the night when I am sleeping, too. I only use heat when I am home on the weekends and awak, or when i get home from work and am awake until bedtime. My catsd just bury themsevles under blankets to get warm. I have a bunch of quilts and blankets I leave on my bed, on the couch, whatever. I come home from work and there will be a lump under my bedspread moving slowly and my cat will be in her own little cocoon/cave in there. So far, hasn't hurt either of them, and they are both 7.