The size of the trailer you need for fulltiming depends upon your feelings about space, as well as those of whomever travels with you. Some can get by with a lot less, some need a 40' fifth wheel (fiver) with 3 slide-outs.
The 8.5' wide Airstream models are just wide enough that slide-outs really aren't necessary. They're just something else to add weight, leak or break and they sometimes block interior access to the whole trailer when retracted (like when you want to use the trailer at a rest stop or truck stop). Compared to most fivers, Airstreams are lighter (yet longer for the same floorspace, given the tongue and behind the bumper hitch), and about 2-3' less overall height with an aerodynamic shape. Much less aerodynamic drag and better fuel mileage. A 3/4 ton truck will do as a tow vehicle. The tongue weight of a travel trailer is 10-12% of the gross trailer weight, and you can shift some of that weight to the tow vehicle front axle with the weight distributing hitch. The fiver pin weight is 20-25% of an even heavier trailer, mostly all on the rear axle. You really need a one-ton dually to be safe with a fiver, not only for the weight carrying capacity, but for stability for the higher hitching point and higher center of gravity of the fiver... even one where you have to bend over in the "upstairs" bedroom.
Yes, you can park a fiver rig with equivalent floorspace in a shorter site, but I personally like a travel trailer better when backing. It takes a LOT less cranking on the steering wheel and less angle on the tow vehicle to turn a travel trailer than a fiver. The fiver does have inherent resistance against sway, but a Hensley Arrow hitch on a travel trailer works as well or better against sway, and doesn't give up the advantages of a behind the bumper pivot point.
How well you can stand full-timing in an RV depends on how much it's like a home. It should have a "real" bedroom with permanent bed, not having to fold a sofa down at night and trying to dodge the cracks between cushions. Unlike what you get with many fivers, you should be able to stand up in the bedroom! There should be access to both sides of the bed, not only so making it up is easier, but so one partner doesn't have to crawl over the other to go to the bathroom at night. Speaking of bathroom, it should have a "real" one, not a toilet and sink inside a shower. The amount of wardrobe space required will depend on the occupants. My wife has finally convinced me that you really need BOTH a couch and dinette for fulltiming. RVs have limited kitchen counterspace and the dinette table across from the kitchen provides more. And, while some folks would feel right at home eating dinner on the couch in front of the TV, most will still want to eat at a table. I personally could've gotten by with the 31 without the dinette to gain the additional wardrobe space over the 30 (both are 31' long), but she couldn't, so we wound up with the 34.
I feel like I'm in a quality home, not an RV, when I'm in the Airstream. It's something that's rugged and that you can take pride in. I know mine will long outlast me and continue to give outstanding service to the probably several owners after me. Just like a house.