
Depends on the breed. My own breed I don't find they want the heat after about 10 days, even in winter, but their whelping box is made into a cave and covered over so quite cosy. I have in fact had more problems with pups getting too warm and having to bring them down to the kitchen earlier where it can be cooler by using the open back door.
Except for breeds that are thin coated I find few breeders now want to use heat lamps with litters born indoors. the heat Pads are less intrusive and can be used so the bich doesn't have to lie on it.