If I were researching fulltiming while shopping for a new rig, I would research service quality and warranty service along with the initial build quality. If I found a unit that I liked, I would call the factory and ask them how they handle warranty service during long term travels (don't say "full time" though, because that could void your warranty). And then I would sock away some extra funds to pay for motels when the rig will inevitably need to go in for service.
And as for the slides...
I looked at a lot of fifth wheels with slides and I don't recall seeing many or any where you could walk from stem to stern with the slides in. We can access the bathroom in ours with the slides in (and that's mandatory to me), but we have to deploy the living room slides to get to the fridge. We also can't walk to the garage with the slides in, but the garage has its own door. The bedroom slide blocks my side of the bedroom closet, but I can just pile my stuff on the bed when we're packing if I don't feel like deploying that slide.
