The first year I was fixing machines, I think I had 10 machines for sale around Christmas. I sold most of them by the last weekend before Christmas. A few for kids to learn on, a couple were coincidental - theirs crapped out and they needed something else, and three to guys up "in the patch"... I guess for something to do on days off?
The next year, I tried to make sure I had a few around this time of year and they went too. The year after that, I think I didn't have any.
This year my patience is a little too thin for the typical local buy and sell buyer ("I'll give you 1/3 your asking price and would you deliver it 40miles to where I am, then unload it, carry it up 3 flights of stairs and teach me to sew?") and the time I took with each customer the first 2 years just wore me out. All 3 of my guys learned to sew from me, and all machines were fully demoed and everyone had unlimited time to ask questions. I think I averaged 2 hours with each person and scheduled them 3 -4 a day at one point.