They don't actually 'poll' the the tower, they monitor the paging channel. They do re-register with the network every 30 minutes or so, so as to let the system know where they are. However, this is for a static phone; a phone moving inside an airplane would be updating its registration every few minutes as it went from one cell to the other.
The ringing tone is sent back by the local switch once the remote party's location has been verified and an ALERTING mesage has been forwarded to it. So, it is not entirely meaningless when you hear a ringtone on your phone.