Update - April 2014

It seems our hosts have changed the options available to us with regards to running scheduled tasks. When the promotion issues first cropped up, I tried to setup a scheduled task that would automatically call the scheduled task processor in vBulletin, but I was unable to call it sufficiently frequently to achieve satisfactory operation.

With the transfer of the domain and hosting from WILL to myself, I've been able to change the server it's hosted on (and consequently gain access to an improved scheduled job manager). This has allowed me to setup a scheduled task that calls the scheduled task processor in vBulletin every other minute. Combined with the calls that are made when pages are served, the system should appear to be quite responsive in terms of promotions.

But you MUST still login and surf around the site AFTER your first post has been approved to ensure that you appear to be active in the eyes of the promotion system.