Router Uptime should be precise to the hour
In the Router Sidebar the Router Uptime is displayed to the user. After ~4 days, it switches from providing hourly information eg "90 hours" to simply saying "4 days". Users often want to know roughly how many hours the router has been up so just telling them "X days" is less useful.
Router Uptime should display a Standard Abbreviated Duration String that is accurate to the hour eg if the browser has been up for 102 hours it should say "4d6h". See #1.