We have been full timing since 2008. We started out with a 38 ft. fifth wheel pulled by a Dodge 3500 diesel. We loved it, but when traveling with other full timers with motorhomes we noticed that they would be setup at least 15 minutes faster than us and I we went to a Walmart for an over-nighter they never had to leave the motorhome. So we decided to trade for a motorhome.
we started out with a 38 ft. gasser. After about a year and a half, I was not happy with the way the coach handled and the noise from the engine and tranny being right next to you. We traded for a 2006 Gulf Stream Tour Master 42 ft. DP. We've been happy travelers ever since. Its been a perfect fit for us. There are two things that we think are important for us for full timing, a king size bed and a residential refrigerator. Now most 40 footers will not have a king size bed and if they do there is very little space on sides of the bed. Ours did not have a residential refrigerator and we had a Nocold 1200 that was a piece of ****, so we put one in. Much cheaper than replacing the Nocold. We don't have a tag axle but the ride and handling was so much better than the gasser that we don't see a need for one. And none of that noise up front when driving. We have been in many county parks, state parks and COE parks and never had a problem with our length. Even in pull thru's we've never had to unhook our toad. Bonuses with motorhome over the fifth wheel was much more storage, inside (because of our 7-1/2 ft. ceilings) and out, and the generator and inverter. We really don't see a need for going longer than 42 ft. or a drawback for being that long.