I think this has been shown to be mythology as the difference in tension in an uncocked spring compared with a @#!*% spring is very small. i.e. in an uncocked state the spring is still in tension, probably around 80% of the @#!*% tension, in order to get a more linear response. If the spring went slack at the end of the movement there would be a huge difference in tension across the travel of the shutter resulting in it slowing down towards the end of its travel.
Steve's right. Also, springs do not look at clocks. Cycling the spring will add to the cumulative metal fatigue, too. But, have you ever heard of a valve spring breaking in an auto engine? In a four cylinder four stroke engine, at least two of the springs are under extra tension all the time. Breakages are extremely rare, as in unheard of.
Al that said, I don't leave either my cameras or my guns @#!*% .
Is there some sort of $%@#$&ing censoring going on? My original post doesn't look like that!
I don't leave my focal plane shuttered cameras cocked (there, I wrote it) but my Bronica and Mamiya cameras are designed so that the lenses can only be taken off and put back on in the cocked state and that's the way they stay.
I don't know if anyone else has said this, but you should leave all mechanics in a position of rest. Store your lenses at their widest aperture setting to avoid stretching the springs, and store cameras un-cocked. If you have shuttered lenses, it's especially important not to leave them cocked for long periods of time, as it will affect the actual shutter speed (rangefinders and some medium format SLRs.)
I don't know if anyone else has said this, but you should leave all mechanics in a position of rest. Store your lenses at their widest aperture setting to avoid stretching the springs, and store cameras un-cocked
The ziplock bag, when sealed, keeps the humidity level inside the bag about as high as it was when it was sealed.
Let's say you sealed it on a hot, humid summer day. Come wintertime when it is cooler the humidity is trapped in the bag but the dewpoint has fallen far enough the moisture will condense on the camera parts. Note that a lot of moisture can accumulate before you ever see it. Once you can see the condensation it is very severe.
You have also created the perfect environment for fungal growth.
Leaving the cameras to breath avoids this issue with seasonal changes.