Hello Annie,
I agree with Amy. Pearls need to be worn to be exposed to air and
humidity but most of all to the last one. However, even the best
quality of pearl will die within 100 or 200 years approx. The need
of keeping them in a safe will speed-up this process due to
dehydration. Pearls are organic and are depending on the numbers of
layers in order to stay the way they are to reveal their luster. As
far as I know, their is no way to “calculate” how many years are
standing to each layer of mother of pearl. To many factors are
involved in this process.
Be aware that the longivity of a pearl can be shortent wenn a pearl
is worn. Human sweat (consistency of sulfur), parfumes, alcohol,
hairspray, detergent and many more, are attacking these layers. The
ideal way of keeping them in teh best condition is to leave them
where they’re supposed to be, but that is not an option, is it?
My best advice (if someone wants to know) is to keep them in the
best condition as you can regarding the needs of this pearl which is
for sure not a place in a safe. Take care about it and it will give
you the best it can. This is not only true for pearls but for
gemstones aswell.
Enjoy and have a nice day
Pedro