When configuring advanced alerts there is the default option to Reset the alert "Reset when trigger conditions are no longer true". But you cannot set a time delay on this reset. This would be an extremly usful addition and should be relatively easy to add as it is an option for the custom reset conditions.
One example of its many uses would be when monitoring high cpu or util on a device, if the value drops below the threshold for one poll then the alert will reset when usually we only want the alert reset when it has been below the threshold for a number of minutes.
It is possible to create a custom reset but it is slighly more effort and the easier it is the better :)
Not sure what version of NPM you are running but at least on 9.5 at the bottome of the reset condition tab (at the very bottom) there is the ability to "not reset action until exists for more than " and then you can set the time to wait to reset that condition.