Salesforce Release and Sandbox

Every year Salesforce have 3 major releases, marked with Spring, Summer and Winter release. It start from Spring, Summer and Winter follow by the year number. But, for Winter release, the year used will be the coming year, example: Winter '14 is release on Oct '13, some users may confuse with this, but that is how it named.

Here is the production release date for last 2 releases (now in Spring '14 release) and schedule date for coming release:

• Winter '14 : 04 Oct - 12 Oct '13
• Spring '14 : 04 Apr - 18 Apr '14
• Summer '14 : 11 Jul - 19 Jul '14

Follow Trust
Check Salesforce schedule maintenance & major release schedule to see plan down time
https://trust.salesforce.com/trust/maintenance

Bookmark/save Salesforce release date
Advise to follow Salesforce blog http://blogs.salesforce.com and Success - Release Readiness community to get latest update on the new release and features.

Sign up for a Pre-Release org 
Usually 2 month before Production release date, users can sign up for Pre-Release instance if would like to try before Sandbox release. If you select not Developer Edition, Pre-Release instance is only good for 60 days, after that will be wipe out.
Example: for Summer '14 Pre-Release sign-up page
https://www.salesforce.com/form/signup/prerelease-summer14.jsp

Understand Sandbox Preview Window
Some sandboxes will be automatically included in Preview to new release and some are not. It depends on your sandbox instance. But, even your sandbox is not in the preview list, it will be upgraded to latest release on the last week of production release, so you cannot request your production / sandbox instance always stay at the old release.

If your sandbox instance is listed for Preview:

• if you want your sandbox upgrade to new release, no action needed
• if you want to stay in current release, you need to refresh the sandbox after a given date 

If your sandbox instance NOT listed for Preview:

• if you want your sandbox upgrade to new release, you need to refresh your sandbox by a given date
• if you want to stay in current release, no action needed.

Sample of Sandbox Preview Instructions for Summer '14 release
http://blogs.salesforce.com/company/2014/04/summer-14-sandbox-preview-instructions.html

If your sandbox is part of Preview window and you use new features introduce on that release, while production still not in the new release. It will cause issue if you deploy the new features to Production, advise to check to the release notes if you have any new features used, because you will not able to deploy that features to your Production instance.

Managing Sandbox
For both full or developer sandbox, set a plan date to refresh your sandbox. Some organization set for monthly or quarterly depend on the business and requirements. Always refresh sandbox when you have major deployment or project within Salesforce platform.

Create a post refresh run-list, example:

• Data Masking
• User/Profile modification
• Turn off schedule jobs
• Manage outbound email 
• Manage outbound message
• Validation rule and workflows
• Etc

Best Time for Major Deployment

• Not during preview window
• Let major deployment stable for a few weeks