Does = 11-12 years average age, but... usually the death in does is kidding related. Does that are "retired" from breeding around age 10 live longer... up to 16-18 years. I just recently found a doe who was 24; she was retired from kidding at age 10.
Wethers = 11-16 years average age
Bucks = 8-10 average age - bucks usually live shorter lives than does and wethers due to the stresses of going into rut each year; this really takes a lot our of them.