As previously mentioned a Pokemons Affection stays permanent but as for Fullness and Enjoyment, these drop as time goes by.
•Affection: Determines how happy your Pokémon is with you
•Fullness: Determines how much PokéPuff your Pokémon needs
•Enjoyment: Determines how much your Pokémon has been played with.
Even if you store a Pokemon in pc, battle box or poke bank. It stays the same.
Here's a rough guide on heart requirements along with happiness meaning (numbers)
Affection Value Small Hearts Required
One Heart 1
Two Hearts 50
Three Hearts 100
Four Hearts 150
Five Hearts 250
Source: Wiki (for heart statistics) + Rest personal experience.
Hope I Helped!