They have them usually every two weeks, early Wednesday Morning. The last update occurred on December 16th I believe. You are correct in assuming that there normally would have been an update yesterday morning but because of Christmas and New Years the last update was a little larger than normal and allowed them not to need to have an extended maintenance yesterday morning.
The Next extended maintenance should occur in the early morning hours of January 6th. I would then expect the next update after that to be on January 20th but it is a little early to make predictions that far in advance.
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Welcome Spring!