Reminding Users to Update Content

I run a WordPress multisite with over 90 editors managing about 50 sites. Every year, it’s important that all editors review and update their content.

It would be nice if it were possible to have an email notification automatically sent out to editors of a site if a page/post/media file hasn’t been updated for X days. Our current solution to reminding people is staggering email reminders by hand to different offices of the company throughout the year asking people to update their pages.

If there is any way to automate this, it would be extremely helpful. I tried searching for existing plugins that have this capability, but didn’t come across anything.