Given that it is holiday season, I would add an additional 10 days to delivery.
Looking at the people that had their prints delivered in August, the average number of working days (based on us federal calendar) has been 68.76 days (~ 69 days). (sample size 5)
My package was delivered on 11/11/2017. Based on the same calculation (removing weekends and holidays), I should expect to hear on 2/23/2018 - which is 5 days before the end of my extension.
This calendar lets you calculate days:
https://www.timeanddate.com/date/workdays.html?y1=2017&m1=12&d1=4&y2=2017&m2=12&d2=4