It's not a hard schedule, I'd say it's "ASAP" - you usually will see a lot if the critical windows / adobe patches within 2-3 days of Microsoft/Adobe release.
Other non critical updates can take longer (1-3 weeks), like an office update for example. Usually if windows update says I need an update, if it's not available with latest PMimport after 2 weeks, I submit a ticket or idea and then the patch team addresses it pretty quickly.
1-3 weeks may sound like a long time, but honestly I'd rather they test in house and release working updates rather than rush and release ones with wrong command lines, etc. I've felt Patch has improved over last few months at releasing working updates (knock on wood).
Here's an example of an idea I submitted where PMImport didn't include KBs I needed that was addressed pretty quickly.
https://www-secure.symantec.com/connect/ideas/please-include-these-revised-updates-pmimport-march-2013
Also, I have my PMimport scheduled to run at 1am every night.
I've found it helpful to set up an an automation policy that emails me if PMImport downloads new updates. So every morning I know if PMImport downloaded updates, and then I know I should check remediation center.
See here for more info on that
https://www-secure.symantec.com/connect/forums/patch-import-updated-can-i-see-which-updates-are-new