If I open parallels and check for updates it says "Your version of the Parallels Desktop is up-to-date". I have 5604 the current is 5608. Why doesn't it try and update to the newer version. Never has. Always had to check and download manually.
Build 5600 is the latest production release. Builds 5604 and 5608 are unofficial bug fix releases that must be individually downloaded. They are best considered as betas on the road to the next production release.