How long do high quality speakers "last"


I am the original owner of a pair of ProAc Response 2 speakers. They are almost 7 years old, but have never been driven excessively hard. How long (i.e. useful lifespan in years) can I expect these speakers to "last" (i.e. no significant sonic degradation) if I care for them carefully? When they do start to degrade, what mechanical failures and sonic degradations can I expect to occur? Thanks in advance!!!
mshan
I bought a pair of Series 1 Bose 901s (closed box, rubber surrounds) I bought in 1972.  My son still has them.  They look and play fine in his basement party room.
Recently I saw a pair of Duntech Sovereign 2001's with all of the bass drivers worn due to age. The cone surrounds crumbled into dust in my hands! Now whether this was caused by sheer age, or due to excessive sun exposure I don't know...but the result is the same. Someone can probably replace the drivers...but it is going to be a project.
44 year old pair of EPI 70’s still running strong; all original including the surrounds. Pretty sure the Pioneer receiver they run on is just as old and with original lamps and no LED crap lights either... still original caps too. Original owner. My teenage son now has this in his room.
Recently I saw a pair of Duntech Sovereign 2001's with all of the bass drivers worn due to age. The cone surrounds crumbled into dust in my hands! Now whether this was caused by sheer age, or due to excessive sun exposure I don't know...but the result is the same. Someone can probably replace the drivers...but it is going to be a project.

Not a big deal. I'll take them for cheap.......