Yes, you can simply log off and technically you've logged off of your Live account by doing so. If you set up a local account and log in you should still be able to see and get updates from the store. I recently flattened my SP and when I set it up I set up only a local account. The store did not know who I was on the first visit - it asked for my user and pass. Since then I've automatically been informed of updates even though I'm logged on as a local account. For me personally that's not so good news as I wish not to be spied on by the NSA every day, but apparently they still get to see some metadata related to my Live account compliments of MS every day