I live in that world by outsourcing article fetching to external services and storing all messages/articles locally. The basic setup is this:

Emails:

• Offlineimap syncs 2 Gmail accounts and connects directly to…
• Dovecot as an IMAP server. Dovecot, stores the emails in Maildir format and Gnus’s nnimap backend gets them from the local Dovecot server.

RSS/Atom feeds:

• A program called Feed2exec saves RSS and Atom feeds in Maildir format. Dovecot monitors those folders and serves them to nnimap along with the emails. There is at least one other program that fetches newsfeeds to Maildir, but Feed2exec is in debian.

All 3 of these services do their job regardless of whether Emacs is running, and nnimap is super fast when the server is local.

I don’t read actual newsgroups anymore. If I did, I’d install Leafnode for them. But I wonder if the nntp backend would benefit to the same extent that nnimap does.

I ended up installing dovecot, along with one of the search engines it can use for server side imap searching. It works really well, is really fast, and didn’t require setting up user databases or any of that stuff.