How to go about checking for updates in pages that load completely only infront of a user?

I am making a chrome extension that checks for the existence of a node in a page. I am using an event handler(DOMNodeInserted, it is deprecated but works for my purpose), but it doesn’t seem to work when the user does not have chrome open(they have it minimised). How should I approach this? Trying to periodically reload the page and check also doesn’t work(b/c the user is required to be present for the page to load completely, hence why I used an event handler in the first place).