If you have not turned on the snooze option, the Samsung alarm clock will ring for as long as 5 minutes. After that, there should be a missed alarm notification.

If you want the alarm to ring nonstop until you manually stop it, you can turn on the Snooze option.

In the Snooze settings, you can change the interval to 1 minute, and then make sure you select the Forever option for Repeat.

With this, the alarm will ring for 1 minute, snooze itself (when there's no human interaction), immediately ring again for 1 minute, snooze itself, and immediately ring again. This goes on, I would say, for as long as no one is touching it.