In the notifications screen, to make a notification stick permanently, we enter 0 for timeout. But after entering 0 for timeout, the notification is shown and then removed immediately. This is because a string value is assigned to $scope.options.timeOut and timeouts are created for notifications when timeout value is truthy. Line#441 in angular-toastr.tpls.js :

scope.init = function() { 
         if (scope.options.timeOut) { 
          timeout = createTimeout(scope.options.timeOut);
        }

The value for timeOut and extendedTimeOut should be numeric. The number 0 is not truthy, but the string value "0" is truthy.