Because we’re still developing collections, I don’t want to promise anything that will change (and some of this will change, because that’s how development works). Collections will end up being both evergreen and timely. I also see collections that are created once and left alone living alongside other collections that are updated frequently.
What’s in the apps right now is only the beginning: but what the team decides to focus on next isn’t finished yet, so I can’t give you a definite on anything. The future will hold more (in terms of diversity of collection topics and people who came make them, among other things) but specifics are still very much in progress.