Perhaps have a look here Understanding Media Duration and how it affects the playback of a Layout
So if your layout is let’s say 30min long - ie the region with the longest duration on your layout is 30min.
Layout will reload each 30min.
Now, if you want your display to show the same layout, you can either set it as default layout and don’t schedule anything - we don’t recommend it, default layout should be something very simple, not often changed so it can be displayed when there are problems with scheduled layouts (or they are being downloaded etc).
What you perhaps should do is schedule an event on Schedule page in CMS.
With end date far into the future, without repeat.