Scotch Stored In A Open Glass Bottle

hello,
i have a beautiful scotch glassware set that i got for my wedding.
i want to pour my bottle of johnnie walker double black in the decanter. it does not have a sealed top on the bottle only a fancy stopper that is not air tight.

basically its like how they use to store scotch in the old days.

will this ruin my scotch?
if not how long will it last in the decanter.

thank you.