New archiving policy not honoring settings

Hello all - thank you for any assistance or comments.

Exchange 2007 SP3
Enterprise Vault 902

Our default mailbox archiving policy moves content from Exchange to EV once it's 90 days old. We have a dozen or so mailboxes that need a 180-day archiving policy. A few of these mailboxes work; most of them do not. Here is how I've set things up.

I created a new mailbox policy (18-months) and set the archiving rule to move content, based on age, once it's 180 days old.
I created a new provisioning group, assigned the necessary mailboxes to this group, and assigned the new 180-day mailbox policy to this gruop.
I changed the order of the provisioning groups, where the default 90-day policy is on the bottom of the order and the 180-day policy is at the top.
I performed a "run now" on the provisioning task.
I performed a "synchronize now" on the mailbox archiving task.

If I go to Site | Targets | right-click Exchange | Display Policies Assigned to Mailboxes, the 18-month provisioning group and 18-month Exchange policy are both accurately associated.

This is where I officially ask for help! :-)