Every comp is different. Some organizers have lots of free time and get the results posted and sheets mailed out asap, sometimes they are really busy and it takes some time. The organizers are typically volunteers just like the judges, so they usually are busy with work, family, life, etc.
Of course it's always nice to get results very quickly. If they said they would get the results posted online somewhere, then by all means send them an email and ask when they will be available. Of course I'd say be polite and don't sound demanding.
It wouldn't hurt to thank them for putting on the competition, sometimes a little praise goes a long way.