As mentioned...either buy a rig with more closet space &/or trim down the wardrobe. Our closet is plenty big enough and we try extra hard to not take more than we will realistically use. Any off season items are kept in the back of a huge corner cabinet.
We actually have too many cabinets...we can pack in too much stuff and have done so then hung our head in shame when we realized it was way too much! We are cleared out now and much happier!
If you will be traveling all over the country all times of the year it does pay to have warm and cold season clothing items handy. We wear sweat shirts almost year-round here. Many times we've needed a coat going to the Rodeo the 4th of July.
Just be real about what you actually will wear and what you just think you want. We are all creatures of habit...we go for that favorite shirt or jeans so do that...go with a few favorites, a few items for an occasional dress up event and get real about how the fulltime lifestyle is made for easy wear comfortable clothes and shoes.