Policies are refreshed on a client when the computer is turned on, a user logs on, an application requests a policy refresh, a user requests a policy refresh, or the interval between refreshes has elapsed. The latter part of that sentence is key: there's a GPO you can enable that will allow you to customize the interval at which computer and domain controller policies refresh. It's best to make this change at either a domain or OU level for consistency.
To enable the policy refresh interval, follow these steps (Assuming you're changing this on a domain-wide basis):
Within the Group Policy Management Console, find the Default Domain Policy in the left pane.
Right-click on Default Domain Policy, and choose Edit.
The Group Policy Object Editor window appears. In the Computer Configuration tree, navigate through Policies, Administrative Templates, and System.
Click Group Policy.
In the right pane, double-click the setting Group Policy refresh interval for computers, or Group Policy refresh interval for domain controllers, whichever is applicable.
Select Enabled, and then enter an interval for the refresh. Be sure to make this a healthy interval; otherwise, you will degrade your network's performance with constant traffic updating policies across the domain. For smaller networks, 15 minutes should be an acceptable timeframe. Allow 30 to 45 minutes for larger networks.
Click OK.