Advanced Security Question

When you enable a password and encryption on a new BlackBerry (or on one that has been security wiped), one of the steps involves pressing random BlackBerry keys and moving the trackball (or trackpad) randomly for a designated length of time. The purpose of this step is to "generate random information for the new content key pair." I've noticed that this step never comes up on a simple password change or even when you disable and re-enable encryption. It only comes up when the BlackBerry is new and encryption is enabled for the first time or upon a security wipe. Why? Would it be a good security practice to wipe the device and redo this step once in a while or would that be totally unnecessary?