In general, the time it takes for changes to your domain to take effect can differ greatly, ranging from one minute, to 72 hours. Most popular hosting providers perform updates on a constant basis, and in many cases if you associate a new domain with your hosting account it should be active within 5 minutes. However, there are instances when people have to wait for longer periods of time, and have even had to contact the hosting provider to force the changes to take effect.
If you are noticing that there is a consistent delay in the changes you make to your hosting account, then you may want to consider changing hosting providers. Do not be afraid to contact your hosting provider and let them know that you are disappointed with the amount of time it is taking for domain changes to take effect in your hosting account.