Hi, you can use either an infrared bulb or a ceramic heat emitter. The infrareds last a few months, the CHE`s can last a few years. So long as the ambient (air) temp in the coolest parts doesn`t go below approx 21c (72F) the monitor should be fine.
And just for the sake of mentioning it, if there are darker hiding places leaving the heating/lighting on 24/7 is o.k, should you wish to do that.