The Salesforce.com Spring ‘08 release is just around the corner and soon you'll be able to take advantage of great new features like  Roll-ups on Accounts, Automatic Campaign Assignment, and Advanced Validation Rule Functions!

We've published a page to help Force.com Sandbox customers plan around the upgrade cycle, and help inform whether and how to participate in the Spring '08 Preview that is offered to Sandbox customers. Whether you decide to participate in the Spring '08 Preview or not, rest assured that your sandbox will remain operational throughout the release window, except during scheduled maintenance windows.

See the Sandbox Upgrade Window page for more information.