[Questions] What do You do With "Extra Cards"?

Hello, you humans of the Internet.

I'm currently re-organizing my Pokémon card collection in order to create a Living Pokédex. My goal is to collect one of each Pokémon and arrange them in the correct Pokédex order. As my collection grows, I intend to switch to more valuable editions. Obviously, there will be "extras" of some Pokémon, as well as a bunch of Energy cards, Item cards, and Supporter cards. My question is as follows: What do you do with additional cards if you have a comparable method of organizing and storing your cards? How do you store them?

I'm excited to hear what you guys have to say!

I collect every card, so I personally sleeve them and put them into card storage boxes after using a collection tracker to log that I have them, since I never know which, if any, will blow up and be a card that's worth $5 instead of $0.20 in 10 years.