I appreciate all the sentiments and comments. Thank you.
I had two more reasons for thinking about replacing the units. The first is we plan a major upgrade to the roof soon to replace a couple of patches, remove two inoperative solar panels, remove many feet of sealing tape, replace a bathroon vent with a second Fantastic vent and add a new white EDM roof. When the new roof is in place, I'd like to stay off the roof the next few years.
In addition when we paint the entire coach this fall, the A/C covers will be painted a matching color, ie why not paint new covers rather than later end up with a mismatched set.
We're enjoying our tenth season in this National MH after starting in 2004 with zero warranty items and nearly trouble free 110k miles in all states (except Hawaii) and all Canadian provinces. By renovating the roof, replacing slide seals and a new paint scheme it will be a new coach to us and should keep us on the road a few more years.