I have cleaned mine out to find enough lint to knit a small sweater, I clean it pretty often but every so often it still coughs up a hairball or two, I clean it fairly often, maybe not as much as some of you do but on a fairly regular basis,
Don't forget to check between your feed dogs as well, sometimes it can build up there as well and they won't work quiet as well.
My new machine is a front loading one, I use the extended table all the time unless I am doing something that has to wrap around to sew it, I leave the door open, that way some if it escapes all on it's own and I can see when it is building up.
Watch using the canned air, it is cold and you can freeze things with it if you over spray.