I leave my Babylock Esante on the whole time I'm sewing and only turn it off when I'm taking a break or done for the day. I have my Babylock for almost 4 years now and light is still burning. I believe these newer machines have those bulbs that burn thousands of hours.
I would think turning the machine off and on throughout your sewing time would cause more maintenance issues over time than the light burning out. I'm not an expert by any means .... just a guess.
Babylock makes great machines - well made and long-lasting. If you have any concerns, just ask your dealer for their expertise.