[Albus]

Thought I'd take a minute to post an 'overview' for those not familiar with vbulletin crons.

When you schedule a task in vbulletin, the time you set for execution is not an interval, but a specific time. For example, if you create a single task and set m=5, leaving the rest of the timing options alone, the task will run 5 minutes after every hour, not every five minutes.

Therefore, you will need to create as many tasks for this as you need. For example, if you want it updated every fifteen minutes, you need four tasks, setting m=0/15/30/45. This is how it breaks down:

For a five minute interval: 12 tasks where m=0/5/10/15/20/25/30/35/40/45/50/55.
For a ten minute interval: 6 tasks where m=0/10/20/30/40/50.
For a fifteen minute interval: 4 tasks where m=0/15/30/45.
For a thirty minute interval: 2 tasks where m=0/30.

This is much more preferable to running the queries on the index because adding a few more row to the tasks table is negligible in comparison.

Hope this answers some questions before they are asked.