In 1989 I acquired a French MAS 36 with a crate of Syrian made 7.5 French, Berdan primed, crate of about 1800 rounds made in 1953.
They where stored in a garage that followed the weather cycle of being hot and humid to cold and dry.
I fired most of them throughout the years with the last fired batch in 2016, with no problem. So, 60 years of good services.
I refurbished the last 500 rounds, saving the powder to be used in reloading my 5.56 and the bullets were reloaded for my 300 blk.