I read up on this several years ago.
There was a guy who disassembled his mini 14, greased it, vacuum packed each piece with a small pack of dehumidifier, put it all in a PVC tube, and buried it in a field near a stump for about a decade. He did the same to several mags and ammo.
After a decade or so he had difficulty finding it as the stump was mostly gone.
The biggest thing he recommended was to not grease everything. It wasn't needed with all the other layers of protection.
If you clean your tools, and vacuum pack them with a cheap desiccant, they should be good for a very long time. Anything else they are in, any additional protection, is icing on the cake.