In Brian Smith’s recent post about the PWA Administrator that you select during provisioning, he points out that there is nothing special about this account — as you know, this account is the first admin in the system. According to Brian, it is also set as the administrator for the PWA site collection:

The first administrator is also set as the primary administrator of the site collection created for the PWA site. You can update the user in this case using stsadm -o siteowner. The parameters for this command are -url -ownerlogin -secondarylogin

My personal practice is to set the PS07 Service Account as this “primary admin” to ensure that it always has access. After provisioning, I log in as the service account and create the other administrators as needed. During post-deployment knowledge transfer, I strongly discourage clients from ever making any changes to the service accounts used during configuration (e.g. passwords, changing to another account entirely). While it’s possible to go through and change all the passwords, it’s labor intensive and error-prone, and any missteps during that process will cause issues in the environment.