Do loaded mags really lose their ability to work after a time? If so , how long would you recommend leaving one loaded?
There is no definitive answer to this other than yours will work until it fails. There are stories all over these forums about people finding loaded guns from as far back as WWI and they still went bang when the trigger was pulled. What seems to be the consensus is that it is better to leave a magazine loaded than to continually load and unload it because it is the number of compression / decompression cycles that shortens the life of a spring and not how long it remains compressed.
Of course, YMMV!