Gary:
You have a very minor case of creeping seals, if it only affects one window. After 16 years, you are unlikely to see it affect any others, or to get any worse on the one it is affecting. When you eventually decide this is an issue that Must be dealt with, check this site:
http://www.daverootrvglassrepair.com/Dave is a real nice guy and will talk to you on the phone. He will send you one of his kits if you want to try the self repair, or if you are anywhere his traveling repair truck is going to be, you can get your window fixed in tune with your travels.
I had 17 windows that had creeping seals when I bought our Contessa, 2 years ago. I bought a double kit from Dave and on our first long stay I got 15 fixed without seriously impacting my time for relaxation and other pursuits. I finally got around to the last couple a few weeks ago, when Dave's traveling guys were in my neighborhood and I could get some more of the "glue" (caulking) that is part of the secret to a successful fix.
the level of skill required is low and Daves instructions are thorough, you just need a helper to hoist the bigger windows down and back up again.
Someone mentioned this being a disease, but there I think the confusion is with blown seals, where the windows get foggy. Since yours are creeping, but not getting foggy, there is no reason to expect this to affect the rest of your windows after 16 years. They would have shown up many years ago. Blown seals can start at any time, especially if the window is mistreated. If none of yours are blown, chances are you won't have a problem that way.