Best way to store cartridges?

I've got a Denon DL-103R that I keep as a back-up cartridge. I'm considering having the the cantilever / stylus replaced, as well as having it mounted / potted in a wood body. However, as I mentioned, it's my back-up. I may not use it for years.

What's the best way to store cartridges for the long run? Air-tight container? Displace the air with N2 (not sure an easy way to do this)? Any other considerations?
I just store my backup cart in it's original packaging. I think it's sitting in a drawer at my bedside table.
If you really want to preserve it for a long time, I would put it into an air-tight container and displace the air w N2 like you said. You could use one of those wine-keeper aerosols or go to a tire dealer who offers N for filling tires. You would probably want to re-fill it every year or 2 since its bound to leak at least a little.
You may never use it again. Sell it, that's the best way to store it.

You can store it at my home, I have four tonearms so one can be it's resting / storage place.

You're welcome to visit and listen to it whenever you wish so you can confirm I'm taking good care of it.
So it does not 'dry out', which will corrupt the stylus holding material. Often the compound is 'rubber' like and will go dry quickly, that is after five years.
I've used a FoodSaver vac-u-seal machine to seal a cart. in its factory box. Once sealed a syringe needle connected to a hose was used to introduce dry Argon into the sealed bag and then the bag was resealed to close off the hole from the needle. Probably over kill, but it did keep any O2 from the rubber bits in the cart.