It depends on the project and the thread. If I'm using my cutwork needles it'll get done either after or during depending on how much cutwork the needles are doing. I just ordered a minature vac attachment set to help clean. I was told never to blow into the machine because you can actually make the lint lodge in places and not come out.

I thought I was doing good by cleaning after every project. "seams" I need to step up a notch.

I had gotten a new machine and loved sewing with it (embroidery machine). So my reliable Singer sat for 8 years. When I went to sew on it, it sounded like a disel truck. When I took it in to have it serviced I was told that machines have to be used. You cannot let one sit. Just like a car in storage, start it up, sew a little. Makes sense. After that and now reading what has been written, I am sure I will be more deligent in my cleaning. I do use the vacuum attachments and love those, they work fantastic. Have had them for years and years.

I use a long handled mini brush to clean the bobbin area and areas deeper inside the machine. It looks like a mascara brush, but with a long handle. Ask your gynecologist for one at your yearly checkup! My doctor laughed and gave me several to use and to give away. It goes without saying that these are clean, unused brushes.
Some makeup counters in department stores have disposable mascara brushes; ask the clerk for a clean one, but the handle will be short.

I love my mascara brushes. When I have one to discard, I wash it well instead and it goes to the sewing room.

See Jenny's video on Missouri Star Quilting. I believe she has a Janome: http://quiltingtutorials.com/browse-...ning-quilters/

I clean mine often as I see lint...I never go longer than a year to have it serviced professionally....