I don't think you have anything to worry about. Modern spring steel really doesn't set like spring steel 50 years ago. And, if the gun in question is a NP, you needn't ever worry.
Definantly not good but might have no effect. I once let my brother take my NP plinking and he put it away cocked it stayed like that for about a week. I dont have a Chrono but it seems like it had no effect on my rifle. However the gas pistons are a whole different animal compared to a metal spring.