How long can you keep a gun cocked?

This has been brought up a few times. Anyway, the design of the spring can be compressed for, well a very long time. Days, months, etc. More damage/wear happens with use or being over compressed or over stretched. Ill leave mine cocked if I know im going to be shooting something. But once I put it away or set id down for a while I will just de-cock it for safeties sake.