I think @Magnus-Holmberg gave the worst case scenario : - ). 30 mins sounds a bit too long in my personal opinion. I helped people with single gateways before and longest I had seen was 15 mins downtime, but that was older model appliance. If you have decent IPS link pipe and 6200 model (even base one), I really would not expect more than 10 mins or so. But, as Magnus said, box does cpstop when installing the hotfix, so that is prior to reboot. Once box is rebooted, make sure policy is correct by running fw stat from expert mode.
The process you listed is as easy as that...just make sure to verify, as it would confirm if there are any incompatibilities with previous jumbos / custom hotfixes (if any), disk space...
Andy
Best,
Andy
"Have a great day and if its not, change it"