If I have played someone a bunch or am on a quest then definitely. Otherwise I try to keep it like live cards. Remember you can always cheat IRL too! It’s up to you if/when/where
I didn’t finish the game because I am still playing gwent haha it’s that good. I would look up which cards you can only get from quests because you can’t get them afterwards. Just look up a mapping for quests to cards (no spoilers of course). I am on mobile and can’t find one currently