It isn't just production fire fighting during the holidays -- it also encompasses test support. My previous company (major financial services) would put a freeze on production changes starting before Black Friday (the day after the US Thanksgiving holiday) and ending after January 1. You would think that would pretty much free up the staff for some much needed rest and work/life balance. Nope. Offshore developers would amplify their efforts now on getting ahead of schedule for development work (bonuses for the contracting firms were at stake). When problems arose (nearly every day), the DBAs would be contacted "just in case it was a database related problem."