I voted your suggestion up, however I would also like to point out that you may be in the realm where a custom database trigger would be better. You *can* manually edit the database value (nodes, interfaces, volumes) table. If you use your custom property as the key, it would be fairly simple to set a trigger to update the polling intervals based on THAT. Then, when the criticality of the device changes, the polling interval can be updated auto-magically.
Just a thought.
- Leon