How long does it take to update House Rules

I am testing various changes with the House Rule Settings (mainly around website categories). I last updated the rules approx. 10 hours ago and the change was to allow the social networking category (previously this was blocked). But when I log onto my daughter's laptop as her and attempt to visit any social network sites I am still getting the blocked page. The settings are displayed correctly in the House Rules (i.e. Social Networking is not blocked). How long does it take to update this, and is there anything I need to do to speed this up?

Thanks

Phil