I grew some apple mint this year, and have a jar of dried leaves. Will report..
Dried leaves tend to lose their freshness factor, imo.
If you like mint tea with a drop of honey (as a lot of people do), I would recommend storing the leaves in honey.
Empty jar.....gradually fill with freshly picked leaves right up to the top ..... pour runny honey over it until jar is completely filled.
Screw on top, tilt jar upside down and back again for a while, to sort out air pockets, then bung away until a dreary winter's day when you are in need of a quick 'summer's day fix'.