Welcome to the forum. As to your question I guess that entirely depends on how good your marriage is
The size or type of RV is totally up to the desire of the owners who choose them. We know people that are totally comfy in a 10' truck camper together.
On a side note depending on where you choose to camp in Arizona you should know that many areas have really mineralized water. Our first motorhome spent it's whole life in AZ before we brought it up to the Pacific Northwest and we learned a lot from that. First the water from around the Yuma area being so mineralized had built up deposits so bad inside the water heater that the temp switches couldn't read the water temperature correctly and the heater kept over heating the water. Then the brass check valve on the back side of the water heater developed a pin hole leak and sprayed water all over inside the rig. The minerals just ate through it.
Spending a lot of time in the desert is a learning experience, ask a lot of questions from those down there that have done it a lot.
Have fun, wished we could head that way after this last round of wind and rain storms (4 in a row) here in western Washington...