I think there is some truth in what stevage said. Usually when we come home the cats get up and are unsettled due to the change in routine. I try to get them settled on the guest bed again before going to bed myself, but this doesn't always work if they're really amped up. If I am able to get them settled, he won't sleep with us (the other cat isn't as interested in sleeping with us), but, if I can't, he'll likely show up in our bed later.

So, it is likely just a matter of getting him comfortable sleeping somewhere warm so that he isn't interested in moving to our bed.

Edit: Having said that, before I started this routine, he _would_ come up to bed if he was sleeping somewhere else already on a normal night in. So, I don't know.