Again folks thanks for all the comments.  You have allowed us to rethink the size of our 5er because a lot of the floor plans we liked were in the 40-43 foot range.  We had ruled them out because of their length but i think this has a new perspective.  

Happy Camping to ALL

the biggest you can afford and still be comfortable  driving or pulling, even with two people they get small after a while, we has a 29ft and then traded it for a 38, much better for us to live in and have some space 

We're very new to Full timing and fortunately we're happy with our 43ft Model A

We've been full-timing in our 40' DP with no slides now for five years. We intend to put it up for sale later this year and "downsize" to a 34' Airstream TT, also with no slides. I say "downsize" as the actual living space in each is about the same. We know people who full-time in a 1973 (yes, 1973) Dodge Van conversion. Whatever you are comfortable in is the right size for you.

I'd suggest that you go to every dealer and show you can and spend some time in every RV you can, no matter the price or condition. Pretend to do all the daily activities, and it won't take you long to figure out what works and what doesn't.

Once you know what floor plans work you can start looking at rigs that have those plans. Yes, there will be minor differences between manufacturers, and those minor differences will guide you to the right one.

As you are looking at rigs, pay attention to how well they appear to be standing up. Remember that they typical RV only gets maybe 30-45 days of use per year, so as a full-timer you will be putting on 8-10 years of wear and tear each year. There is a reason why many fulltimers with towables have heavier coaches. Structure and quality are heavy. Before we bought our Foretravel we met a couple who had started fulltiming a year earlier. They bought a "popular" MH brand new. Less than a year later they traded it even-up for a 10-year-old Foretravel because they could see that their original choice wasn't going to stand up to full-time use. No, they never told us what that "popular" brand was.

If possible, go visit the factory of any brand you are considering. Even if you aren't going to buy a brand-new rig, seeing how they are put together will go a long way toward telling you what you might be comfortable with.

we are seeing many people who are full-timing are downsizing to smaller RVs because of the problems and "scary situations" some of the bigger ones encounter"...…. We are in a 40 foot Montana. We do not know what that statement means.  We purchased the biggest 5th wheel we could afford a 40 foot, 4 sides  Montana.

Wife had never driven anything that big but was a pro in a very short time. We are not "full timers: as we have a S&B but spend most of the year in the 5th wheel.