The RMa's don't use foam surrounds, so I would investigate using a high quality rubber preservative on the butyl every 2 or 3 yrs or so to keep the butyl from drying out (micro cracking) and will help keep them pliable...there won't be any change in sound or performance when you apply it or anything, but it's a worthwhile investment for what little it costs. Be sure to keep your speakers out of the sunlight, even through glass. Not only will it begin to mar the finish over a decade or two, but if you leave your grills off it will slowly degrade driver materials and surrounds as well, IME.
If you're worried or just want to know what your fall-back options might be, give Lou Hinkley a shout and see what he offers in the way of refurbishment (or what drivers or materials he'd likely be able to send you, if you can do that sort of thing yourself)...it might be well cheaper than replacement if push came to shove.
If you're worried or just want to know what your fall-back options might be, give Lou Hinkley a shout and see what he offers in the way of refurbishment (or what drivers or materials he'd likely be able to send you, if you can do that sort of thing yourself)...it might be well cheaper than replacement if push came to shove.