While I hope everyone has a great Christmas and New Year, I usually get bored of typing such sentiments in every email for at least half of every December. When someone does it to you, you have to return the wishes or it looks as though you hate them.
The extra time adds up I reckon, especially if you get a lot of emails.
I haven't been seeing much of it yet this year. I reckon it will start next week, but that only means 5 days of repeating the same long sentence - which is less time than previous years, so I am very happy! :)