Preserving mint luster

I have a coin with so called “mint luster”. It is predictable that the mint luster can be overgrown with a patina/tarnishing. How should I preserve it? Is putting it into a capsule enough?

A capsule is good, but you should store it in a cool dry place as well.

I store my collection in a cool, dark and dry place but some coins (especially UK 50p coins) still tarnish, i put them in lindner trays but I still happens