How long should high quality speakers last?

I have a pair of Snell Type C bought in the mid '80's and a pair of Large Advent Utilities purchased in the late '70s.  Both have had new surrounds installed years ago, cones are still in good shape.  They still pack a punch.  I use a 400 wpc amp with high dynamic headroom on the Snell's. 

If you're not buying them out of the back of a white van legit brands will last as long as we use them within their designed purpose. 

@guscreek ...I remember the DCM TW2Ks'....they lost out to a pair of Infinity's at the time....which lost out later to ESS AMT 1B's....of which the Heil design has sprouted up in variations in quite a few cabinets since....

I've got 4 of them now ( the big Heil's ) with little regard for much else at this juncture and age of the listener.... ;)  

We've all got our preferences....*L*

Lots of great details and suggestions about cone driver speakers.What about electrostatics?

I own a pair of Ohm Walsh LE 5's that were rebuilt before I bought them. I also own a pair of Martin Logan, Summits which I'm the third owner of and I'm wondering if there's a way yto maintain them that'll extend either the life or the fidelity.

I've heard talk of c leaning and even replacing panels. I'm curious if there is some kind of maintenance for electrostatic speakers in general.

A lot of variables here. A five dollar single driver with a rubber surround speaker should last almost forever. A speaker system is a completely different animal. The Capacitors in the crossover can blow at any time, but cheaper capacitors can be more problematic.