This is a bit like me - I have a great boss, and he's been the only one I've had at this company, and I know the next
boss may not be as good. Despite all the work and time away from home, there are some good things about my job (my boss, I come and go as I please, I'm comfortable, etc. etc). Moving to a new company means starting over with a new boss, and the next gig may not be as great. There's no reason to not think it will be as great, but you never know until you're there.