The health issues sound horrible. I know aging is something that happens to all of us, but it stinks when it does. I've had my own bouts of "Oh, that's what they meant!" regarding joint pain, but not the issues you describe.
As for this:
There are several active kite forums, and activity seems to go in cycles. Currently both Kitelife and GWTW Forums are more active than the Rev forums, although that can always change back. I think several things contributed to these forums dropping in popularity. The site took a big plunge after the revkites.com site was redesigned to be a more traditional sales site, they moved the forums to revkites.net which broke all the existing links, broke the ranking on search engines, and otherwise made it harder to visit. The expiration of the original rounds of patents (by several groups) also meant more competitors have entered the market, so while Revolution kites is still by far the biggest brand, they're no longer the only player on the field. There is the natural ebb and flow of the web, where content breeds more content and stagnation breeds more stagnation. Combine them all and the RevKites forums have dropped a bit in popularity for now.
The cycle will likely change again over time, different web sites ebb and flow in popularity.