Yes, using subkeys and rotating them is good practice. But really the hardest problem with pgp is getting people to use it in the first place, so let's not focus on subkey use, or upgrading from sha1 to sha256 (or better), or key length (the author uses 1024 bits only).
Though I'm not sure why the author focuses on non-threats like known plain text attacks, which gpg isn't vulnerable to, and not these issues.
Some misinformed info in there about not starting your messages with obvious niceties "Dear fred" or including the same text at the bottom of all your emails (your email signature). If the crypto is good, this doesn't matter - it's not deterministic encryption. If it can't pass a known plaintext attack, you shouldn't be using it. GPG does.
https://we.riseup.net/riseuplabs+paow/openpgp-best-practices...
Edit: nevermind, i see you meant the site with the tutorial, not key exchange