It is a nice poem with lots of description of Christmases gone by. From boyhood through teens to a mature age, the poet recalls the way he had spent the Christmas day. The merriment, gifts and the sumptuous dinner do not change though.
Imagery-
Imagery is visual bringing up the pictures of past. They show a teen smoking under the cover of snow among others. Teenage is an age of adventurism for both boys and girls. Especially with regard to what is ill-advised.
Flow-
The poem sounds good with consistent rhyming and rhythm. So the flow is easy and spontaneous to the ear.
Tribute-
The last lines pay a deserving tribute to Christmas which is being celebrated as long as man lives. It is a symbol of faith and celebration of life.

Write on!