Well, it starts with proper planning on the site's behalf, like how long do you expect users to use the game service - in years, for example. There should enough idle content for whatever number of years, then features that kind of take care of things from account creation to that point in time. Past that I think welcoming back users with new content, patches, and game lore is smart. But if they drop off then whatever. They got enough out of the site experience.
What I do not like is content or features that really dates a site to specific staff or "eras", it gets very disorienting as a returning or even new player.
In answer to your original question tho, low effort sites are awesome compared to ones that release tons of content that feel immensely hard to catch up with even paying monetarily for the ability to collect or archive stuff. At the very least, if you have a site that have tons of content releases, please just have a historical section or a good way to track content releases so that returning players aren't being slammed with tons of changes in one go.
Not so much a tl;dr but.. I like virtual pet games kept simple mechanics wise that are easy to get back into, as opposed to coming back to a bunch of content and updates I have to spend months and lots of $$ to catch up to, to even become an active account again.
