Projector recommendations?

We are planning to buy a projector for training that we provide to clients all over the state.  We'll be running PowerPoint and video clips off a Dell Latutude D810, so compatibility issues shouldn't be a concern.

 

Primary issue for this unit will be reliability.  I absolutely want to minimize the possibility of having to tell a room full of doctors and nurses that we can't do the training because the projector bombed out on me.  Durability is also a big deal, as we'll be transporting it to each training location.  We need high light output, as room sizes vary from small classrooms to auditorium-sized spaces, and exclusion of ambient light is sometimes a problem.  Also need a unit that handles the heat exceptionally well, because the training is an all-day thing (six one-hour blocks with breaks in between).

 

I've been through all of the comparisons and tech specs on models from the 2300 through the 5100.  On paper, any of them will meet our needs.  I'd appreciate thoughts from the community and/or the moderator on what to get, what accessories will make it work better, etc.