One thing that's come up a lot recently is the change to story content delivery in Guild Wars 2. The new story episodes are free to play during their release windows, but after that require gems to unlock. Some folks are finding it hard to keep up with the release dates if they're not currently playing the game actively. There's a fairly easy way to keep up with the content, even if you're NOT currently playing much (or at all), and avoid having to pay for the content if/when you later return to the game.
1. Get an email update each time new content is live and needs to be unlocked.
You might have unsubscribed from the ArenaNet mailing list if you're not actively playing. Resubscribe! That way you'll get an email on the day new content goes live, and you can log in and unlock it. For example, today I got an email titled " Log in Today: Seeds of Truth Begins in Guild Wars 2!" Fog also makes the process easy by posting in the News & Announcements when a new episode is unlocked, but I also get the email updates in case I miss the GSCH announcement.
2. Log into the game.
You need a level 80 character to PLAY the content, but logging in with any character will unlock it for future use across your account (for when you next play or when your character/s reach level 80). There seems to be some confusion about unlocking vs playing. Simply log in to unlock; level 80 is only needed to play the episode, and that can be done at a future time once it's unlocked.
3. Log out.
It only takes a few minutes, but it saves a whole lot of money later on. Since there's no ongoing subscription, if you own the game, you can always log in when you want to.