Send notification email after change value (delay)

[Krists]

Hello,
I have simple Event-based script (in SL) who sends an email when the status changes in a particular group. This code works pretty well, however I have two questions:
1. Why script works even when the status has not changed. For example, the controller performs a daily scan - and at that time scripts work and send a notification. (status has not changed). How to fix it?
2. How can I put a delay on sending notifications? This means, if the particular group status has switched and is unchanged for 10 seconds, then only send a notification.

Code:

value = event.getvalue()
mydata = storage.get('myobjectdata', 2)
if value then
  if value ~= mydata then
    --email for ON (1)
    subject = 'Main switch = ON'
message = '\nState: Normal'
  mail('1234@yyyyyyy.ww', subject, message) 
  end
else
 
  if value ~= mydata then
   --email for OFF (0)
    subject = 'Main switch = OFF'
message = '\nState: ALARM!!'
    mail(' 1234@yyyyyyy.ww ', subject, message)
  end
end 
storage.set('myobjectdata', value)

Thank you.