You are right about how tough UV is on vehicle paint in the SE and SW states, and that inside storage makes a big difference.
But consider the cost. If inside storage was only $200 per month, in 7 years the out of pocket would be $16,800. Plus the aggravation and time of driving to and from storage every time.
If a company produces vehicles that often stay outside, the finish should last more than six years. That's fairly easy to achieve with the 2 component urethane paints that have been available for the past 40 years, especially on vertical surfaces.
