My Bernina 440 had her last yearly maintenance a bit more than a year ago, but I'm going to wait until summer to take it in next. I don't sew on it nearly as much as I used to since I now have a separate quilting machine and my vintage machines! I wish the newer machines were as easy to service as my vintage ones. I can get into all the corners on the old machines and on my multi-needle embroidery machines, but my Berninas are sealed up so you have to take them in for service
I do take my serger in for maintenance each year. I do lots and lots of baby things for charity mostly, and the flannel generates a huge amount of fluff. I work hard at keeping it cleaned, but there are parts where I can't get into it. I've learned to just schedule the maintenance for when I'm on my summer vacation!
Pam