If you use Verizon, at the beginning of the call you will be told "This call is airtime free." In other words, there are no charges associated with using that code. As for how often you should update, the official word is to do it every three months.
Another cool code for calling other Verizon subscribers, press the * key to bypass their voice mail message to go directly to the tone and leave message.
With the Forced Update; is it *228, dial, then press 80? I tried it both ways and I still can't download a new PRL list. I just keep getting the same-old message that my phone couldn't be updated at this time.