I doubt anyone really knows the typical longevity - triggers mechanisms seem like the most prevalent breakdown after continued use. I suspect the main thing is quality control out the door. As long as the design is a proven (knock off/copy) of a proven design and the parts were built with standard grade materials, there is no reason why we can't expect decent longevity with proper care. The downside is these guns are not easily serviced without robust parts market. I personally wanted to avoid alloy receivers and that was a reason I didn't want to pick up something like the Stevens 555.