NHibernate slow "warm-up"

If I had to pick the thing that annoyed me the most about NHibernate (other than being so typeless on queries...), I'd had to choose: "the slow warm-up".

This is a problem that only arises when you start mapping too many HBMs. We're currently mapping over 60 HBMs, and the factory startup is taking something like 30 seconds on our dual core developing workstations. This as a negative impact on the development cycle.

Yes, I know, I should find out the solution first, and post it here. But as usual, I'll start googling for this soon after the posting of the question. This is supposed to be a diary, right?