It will be different for everyone. You should record your practice with some of these problems. If it sounds good then it's probably fine. Your body works differently then others.
For now I use the drone on my DB-60. But, I guess the real question is I don't feel that an electronic drone is stable, and doesn't have over tones. Jeremy- do you think this matters?
Anyone have any words on using electric drones to tune scales and rep? Maybe using open strings and your natural ear is better? For some reason using something that runs on batteries freaks me out.