[BryantD]

A lot of people replying to this are talking about how holidays are their low period. I work in mobile; the Christmas holiday is the busiest time of the year for us because that's when everyone gets their new devices and downloads apps and has all day to play with them.

Github's a service provider and I would be surprised if none of their customers didn't have peak traffic over Christmas for this or a similar reason.

In any case, I agree with nixgeek; you shouldn't ever expect outages when upgrading infrastructure. On the other hand, you also have to measure the pain of fixing an outage, and that's likely to be higher during the holidays because of availability.