I leave mine on for duration of my time in the sewing room. One thing about computers - they say turning them on and off is not good because it causes the circuit boards to heat up - then cool down - then heat up again, and light bulbs similarly, you can do more damage with the on-off every few mins than leaving it on. And every time you turn it on, it goes through a programming phase - and I would think (and do) if you are gong to use it soon, leave it on until you call it quits for the day. :-)
Marysewfun