As a cheapskate selfhoster who can only afford a few gigabytes of storage, It may come to a point where 30GB would not be enough to host the entire post history of the lemmy fediverse once user activity rises, and only those with deep pockets would be able to host archives of lemmy posts, just like usenet servers.
Meh, storage is cheap, you can get TBs of storage for less than $100. If things really pick up and you're a smaller Lemmy instance, I bet there'll be some good ways to filter exactly what you store on the server.
Well, I am hosting this instance on a VPS, also given that I currently reside in a third world country, my pay is shit that I cannot afford more storage. If there comes a time that I would have to delete some posts and comments to free space, given that I still have not explored the Postgres database container, I hope the devs included some foreign keys on the comments table that would make deleting stuff way easier.