In response to your question regarding salvage life, neither of my two older mains (carbon tape/kevlar or kevlar tape/kevlar) would have a salvage value. The carbon tape sail that we retired at the end of our 2008 season is still good for day sailing, delivery and crew training races. But I wouldn't have the heart to take money for it.
I can't compare to your sail program. We have a 15 race Wednesday nigt series that is taken very serious by our club along with a regatta series that is another 14 races. We race in 6-8 of those regatta series races along with all 15 Wed races plus two long distance races (off shore - type) one 140 mile and one 53 mile race. One main is used for all races for 4-5 years. If and when we start doing Nationals, we'll propably consider a two main program such as yours.