The thing to remember is ethanol fuel is what kills them. I doubt you can find fuel with out but the lower the Ethanol percentage the better.
Also it depends on how hard your pushing them. If your tuned to the max and running 80-100% duty cycle they would kill over quicker as opposed to only being worked at 60-70% their whole life. Why do you ask if you don't car to elaborate on the subject a little more. If your trying to figure out what injector to buy then don't consider them. Go new style 555, (615cc actual) or 740's. Also look at some of the newer top feed options.