Since its getting winter I was thinking of keeping the heater up but I need to know how much degrees it can live.
Some hamsters can live in high heat and some cant. It is just like us, some of us can stand a lot more heat than others. Just take a look at your hammy and see if it is behaving differently. There is no special number that can be put with this, just use your best judgment.
Last winter my hamsters did relatively well with it being cold, but they live together and they huddled inside their castle and slept most of the day.
Hamsters thrive in temperature between 65 and 80 ° F.
Any less, your little hammie might decide to "hibernate"; any more, he might get too hot.