vbulletin search times for different user groups
 

I need to change the search options for different user groups and I can't seem to do it. for example for registered users I want them to be able to perform a search like every 5 minutes or so and paid members to be able to search every 30 seconds or so.

Seems I read a thread either on here or vb.org and now I can't locate it. any help is appreciated.