Being Sonus Faber uses Scandinavian drivers(as far as I know),they probably have rubber surrounds,but can't say for sure.If nobody responds,you may have to contact them.Either one shouldn't need maintenance,just as long as they're kept out of the sunlight,in room temperature, just like anything else.Of course the rubber surround ones seem to last a long time.I have rubber surround speakers that are 20-25 years old,and still ok.Some foam ones lasted as little as 7 years. Foam deteriorates on their own,no mater what you could do,which basically is nothing as far as maintenance goes on either surround type.
