I have a bunch of guns that have been cocked for up to 130 years without any damage. Maybe next year, one of them will have a broken spring, but so far so good.

Have them for ejector guns. Pass for extractor guns.
 

The springs are not the issue. It is the stop plate for the ejectors that are a reason to have snap caps.

As I see in an example hang tag:

"If the gun is fitted with our automatic ejector, it is an excellent plan to have in the gun two exploded shells, so that when the gun is opened and the injectors operated they will have some work to do; other-wise the force of the blow occasioned by the ejectors being thrown against the stop plate tends to batter them and injure the plate."

Quoting from the far right tag, final sentence:

http://parkerguns.org/forums/attachm...4&d=1477448771

Cycles kill springs not whether they are stored under tension or not.