How long do high quality speakers "last"

Depending on your budget and changing tastes,there is a great alternative to expensive future replacement of your component speakers.There is a process called reconing as where you remove your old speakers from the cabinet and send them to a reputable company.Proper reconing will make component speakers sound brand new again ,will have the life of any top level speaker,is the same exact speaker that came with your cabinet,and will be alot less expensive than a manufacturers'replacement.Try this site more info. www.nauticom.net/www/speakers

If you have foam surrounds on the cones, expect them to rot away eventually. Check periodically. It can be repaired. If you drive them hard with amp clipping, expect to cook a voice coil or have the coil former start to rub and buzz. A balance between amp power and speaker rating can reduce that chance. Read the instructions for your speakers. Quality speakers last for decades if used within their comfort zone. Maybe you should consider some kind of high output/efficiency speakers for just rock.

I have had one reconed. Have had some 20 years.  "Quality speakers last for decades if used within their comfort zone." I sold one pair which failed but a guy who was there told me that they were on the floor and they were bouncing up and down before they went.

Much will depend on the owner's treatment.

Otherwise, all excellent suggestions as above.