There are folks who comfortably full time in truck campers. So size is only what you make of it.
Eventually, DW and I know we will have traveled enough and be ready to start staying put for a week at a time. When we do, we will be ready to switch back to a FW. While we know we will boondock a lot, we also know we will want to stay in a lot of NPs. To make it easier and not have to be so selective, we have already agreed to shoot for a 30-32' model with only 1 or 2 slides. The stand up bedroom is nice, but we will probably go with a short bedroom to keep the height below 12'. On the back roads we travel, we seem to find a lot of 12' bridges.
Additionally, we travel prefer back roads so the length plays a factor there. We had a 35' FW and while I never really had a problem, one about 3' shorter would have made it a bit easier. And yes, a 10% reduction does make a difference.
Last thing to consider. If you like to stop and have lunch for the day during your travels, take into consideration access to things like the bathroom and refrigerator. It becomes a real pain to have to run the slide out just to get a drink or use the restroom during a quick stop.