Loudspeakers - how best to prolong their lifetime?

Another thread, regarding obtaining speakers "for life" got me thinking about the lifetime of our speakers. Let's assume, for the sake of the argument, that we have a set that we really don't want to lose (just what I own right now). Is there anything that one can do to prolong their lifetime? We'll assume that we look after them regarding the power that we throw at them and that we don't play them excessively loud and blow the cones.

I recall my first "real" speakers, which were Castle Kendals. After a few years in storage, following an upgrade, I went back to them to use in my third system. They sounded terrible when I connected them up and the removal of the grill showed just why - the cone's foam surrounds had disintegrated! I pulled the two sets of spares out, ones that I had obtained from Castle as backups, and they had also gone belly-up. My current speakers have glass-fibre reinforcement so I expect some longevity.

Is there anything to do or do we just have to take what we are dealt?