Here is an article that has just been published around updating/patching your farms with minimal to little downtime. We look forward to any feedback you might have on the article.
This has been tested in our labs and we look forward to hearing from you around your experiences with performing patching in your environments.
Here is the link to the article http://technet.microsoft.com/en-us/library/hh495476.aspx
Please fee free to email me with any comments, questions or concerns – Aaron.Saikovski [AT] microsoft.com