Treating speaker cones

Someone told me that there is something to put on my 15 year old KEF speaker cones to extend their useful life.
Anyone knows what fluids can be used to keep the plastic and or cone in good shape.
I figure bodily fluids work extremely well. It's easy to obtain them if your speakers sound realllly good.

15 years old, probably too late to extend, probably gone. Look to manufacuter to recone. I do my JBL's every 10, even though recomemded every 5.
dcaudio: i think the liquid you're thinking of is glycerin. it's at least worth trying. could be your speakers have been in a coastal environment all those years. -kelly
Foam surrounds need replacement often. Fortunately for you KEF uses Butyl surrounds, which last a long, long time. If the speakers sound fine, I'd sit back and enjoy the music. Apply chemicals to cones and/or surrounds is iffy at best.
That should have read "applying" chemicals. It is 7:00 A.M. and I'm not running on all eight cylinders yet. Need more coffee.
Thanks everyone. Seem as I may have listened to too much to Mr. Magician. Speakers still sound fine. But the audio bug makes me continue to think about tweaks.
I use Maguires tire dressing on my speakers-keeps the butyl from drying out and for speakers sans grills it adds a nice shine.
One thing to consider is that when a driver is treated, most people only treat the front. Unless the driver is removed from the speaker(how many people do that?), the surround and cone will still dry out. As you have butyl rubber surrounds, and I am presuming polypropylene cones, they should last a long time. And I question whether anything can be used to dress polypropylene, and have an effect. It is a very inert polymer. Unless the cone was plasticized(which I kind of doubt), putting any of these chemicals on the cone does nothing, except make it look wet. By the way, platicizing is the process of mixing a very high boiling solvent in with the polymer during manufacture. It makes the polymer softer, and pliable. The solvent(plasticizer) takes years to evaporate. Which leaves only the polymer(which was hard in the first place). That stiff, brittle polymer is prone to cracking. If the drivers are not of a common size/design, think about a having a replacement set on hand(kept in a good environment, where they will not degrade). That is, if you don't plan on moving to different speakers when these go anyway...