If gunmakers don't want their springs set to rest, then why do they provide snap caps and why do Purdy mainsprings go to rest when one removes the barrels?
That being said, I have worked on thousands of V spring guns, most were left cocked and all but a very few functioned perfectly. Many an antique comes into my shop and aside from hammer guns, most are cocked and they work well. If a spring is made from proper steel, the limbs tapered and parallel, no nicks left anywhere and polished properly, then heat treated correctly, they will function for many decades. It must also be mentioned that flint and percussion period springs did not have the more consistent quality steel of the mid nineteenth century, but they performed well. One never knows if there might be an inclusion in the steel.
The cases where I see broken springs is commonly in Spanish guns. The springs are poorly shaped with horrible taper but despite that most of them work.
