I don't think 55 is extreme for everyone. We keep our thermostat at 55. We live here in Vermont where it was 16F this morning. In comparison, 55 is rather toasty. Our main reason for keeping it this low is frugality. Oil heat is darn expensive, and we don't have an easy option for any other heating source right now. Also, using oil, I'm aware that we're burning a fossil fuel. I am not comfortable turning our thermostat up any higher than our minimum comfortable temperature.
My kids are used to it, and so am I. The kids dance around in pretty minimal clothing and hardly ever complain - if they complain, we have more clothes, blankets, warm slippers and socks, hot tea, hats and mittens, etc. You do get used to it, especially when you're not going back and forth from hotter to colder (like my poor DH who works in a 70F+ office and comes home to 55F - he feels it much more than we do).
If someone is sick or really complaining I will turn it up to 60 to get the chill off and then turn it back down to 55F.
Anyway, I'm not crazy, and I don't think people who keep their thermostat in the 50s are necessarily nuts (and I resent that implication, which is why I'm replying here).
Definitely 55F feels cold if you're used to warmer temperatures. And in the summer? We don't have air conditioning, and it gets really hot, 80-90F, and humid, and we just live with it because there isn't another option (only fans).
However, to the OP, I think your issue is less about the exact temperature being reasonable than it is about your relationship with your DH. You both should be willing to negotiate a temperature that is comfortable for you and feels reasonably frugal to him. I don't think it's wrong to be frugal about home heating. If your lowest comfortable temp is 62F, then that's what it should be, especially if you're the one home all day with the kids. I think your DH should be part of the decision because he's working hard to earn the money (presumably) and I would guess he probably is the type who feels most appreciated and valued when he sees you being frugal with his earnings.
Anyway, more than 2c worth of my opinion, but in any case, good luck.
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