Do you receive all your mail on time? Have you confirmed you have the correct address at you adsense account? Maybe someone is stealing your mail or something, that is not normal IMO.
I think there is no need to worry about it, if you fail your 3rd request then u can still contact them and ask for help about it.
It is ok and it depends on postal dept. service and need a clear address. If you are unable to get it even after third time you can ask for phone verification.
No need to worry. If it doesn't arrive even in third attempt, G will arrange some other way to verify your address..
if you do not receive you PIN after third request, Google will send for you a link to contact with them. And then, you need to send your ID gorverment attach with mailing contact. and then your account will be active. good luck. one day my click cost make $ 8.09
I also faced a similar situation... didn't get my pin despite exhausting all my tries... finally got my payment released by verifying the address