Hello Cap'n Jim! Good to hear from you! Black powder apparently has a very long shelf life and it is the reason that collectors have to be very careful if there is still powder in these shells. Most of the time, it gets washed away or mixes with earth and becomes inert. That being said, there have been people injured or even killed when dealing with these. The small grenado I posted is the only item I have that I know still has powder present. Years ago, I owned a very old coehorn mortar shell that someone plugged the hole with lead. Was it inert? I never found out, which is a good thing! Sold it a few years later. I know there have been places in Europe where old mortar shells from the 18th and earlier are found and the bomb squad is usually called in to safely detonate them.
Here's the sad story of a colletor who wasn't so lucky-
https://www.nbcnews.com/id/wbna24441427