B&W and deteriorating Kevlar drivers

I have a pair of B&W 802N's purchased new when they first were introduced. Over time I had noticed a slight "card board" sound in the upper midrange that seem to grow over time. Just replaced the Kevlar midrange drivers and the distortion left........they need some break in time, but I think I solved the problem (not the cross overs). They certainly changed color over the years from yellow to almost orange. I would recommend the replacement of the midrange drivers if you have the original 800 series.

Anyone else have this experience?
Not me as they're rather expensive for me. and I also don't have the space for them. I have owned the 602's and currently own the CM7's. My 602's held up well and I sold them to a lucky Agoner after 12 years of enjoyment. I didn't notice any issues with my kevlar drivers on the 602's but that doesn't mean it wasn't there. Maybe that's why I sold them. I'm sure if it happens with the mid drivers, it can happen with all the kevlar drivers in their lineup.
Just curious where you live. Could it be the climate and the humidity (or lack thereof) that is a contributing factor in this? Just wondering.
Are your speakers exposed to sunlight from a window or skylight? It could be that the Kevlar broke down 'chemically' due to exposure...just a WAG.
Kevlar does have a 'honk' as some critics have described it.
It was used for it's great strength to weight ratio...personally, I do hear the coloration somewhat.
In the THIEL CS5, Jim's best work (I haven't spent time with the 3.7 which gets raves) he used a Kevlar midrange, but I didn't hear the same coloration. Of course he was using it across wide bandwidth, at 6db per octave it would have seemed to show any weakness in the frequency extremes, EXCEPT for the fact that there were so many drivers, 1 Tweet, 1 Dome, 1Kevlar, and then three paper woofs,(or composite, damn I'm so old I forget things like this too easily). They may have been a plastic coated, paper, OR maybe a poly.

Again, didn't hear that 'honk'.

BTW, the sunlight thing...is that a possibility?

Thanks for the comment. The speakers are in a sunny room, but not in direct sunlight. You can see pictures of the room and system in virtual systems. http://forum.audiogon.com/cgi-bin/fr.pl?vevol&1262106902&view Humidity not unusual....Phila area.
I have experienced this. The aramid fibers (kevlar) in the main drivers do appear to "age" over time. They change color and I also noticed the "papery" coloration in the upper mid-range gradually become more pronounced over an 11 year period.
Aramid fibers such as kevlar degrade in ultraviolet light, so sunlight may be the culprit.
I am curious if you always had the speaker grilles removed? I have not noticed any driver degradation or discoloration on the mid drivers but 99.9 percent of the time, I leave the grille covers in place. I get morning sun in the summer months but have shade screens and shutters on the windows to reduce the light.
yes, Rhljazz, the grills are removed. Thank you for your response, Layman. That is exactly what had happened. I have had the speakers at least that long. I'm glad I'm not as crazy as my friends think!