Well, for a very long time I resisted having any animals even in the bedroom as visitors! I had had allergies all my life and asthma as a child (and now again in my "advanced" years). Gradually I seem to have built up a resistance to cat hair, and the cats just sort of ended up on the bed, the dressers, the TV table, curled up on the floor with their favorite dog, etc. I think if ever a burgler tried to come in through the window, he/she would end up flat on the floor trying to wade through the density of warm bodies!
I guess the on-the-bed thing would never have arisen, because most of the cats had already some cat-training from their mothers and actually enjoyed other-cat company. But last winter (1999-2000) people began to bring me real nursing babies, and I reared them by hand without benefit of a lactating female cat. They all 6 attached themselves to me, rather than to cat-models, and most of them remain extremely bonded. There were lots of things that they didn't learn of cat lore, and even hanging around some of the older cats hasn't broken them of their fixation on me as mother.
And truth to tell, I respond to their dependency and love. The bond is definitely a two-way street!
So the cats on the bed are these little ones, now over a year or a year and a half old.
As to hot, boy are they. In the summer I have to keep easing them a little away from body contact. They are like small, furry furnaces. But in cooler or cold weather, it means I can save on heating bills. When I am up, they are on my lap or lying across my feet or curled against my back, depending on where I am sitting, and in bed, they keep my feet gloriously warm as well as acting as heating blankets for my back and legs. If they cost more in airconditioning in the summer, they certainly save an equal amount of money in winter heating.
But they do guard their individually preferred territories and will vigorously defend them against the older cats (not to mention the dogs, who are not allowed on the bed at night)...
I do think some of you are so lucky with your signif. others. I takes a lot of understanding to accept a load of cats or dogs on the bed at night. On the other hand, I really do understand people who would just not care for animals in the bed. But I have to say, I used to toss and turn a lot, but, like one learns if one takes a new baby into the bed at night if it is still nursing, the body seems to adjust to being very careful not to smother infants. Just as we filter a baby's cry for content and just screen out all the noises that are not threatening -- and leap out of bed at the slightest sound that means baby suddenly can't get its breath -- so, too, we seem to instinctively program our bodies not to roll over on the cats.