Often I start working early in the morning, and might do some guitar tracks where I'll use the M147. Then 4 to five hours may go by, and I'll decide to add more, or, there might be a vocal session where I also want to use the mic. In these cases, is it better to just turn the mic on in the morning and turn it off at day's end, or keep turning it on and off throughout the day? I guess I'm wondering first which is better for the tube, and secondly, which is better for sound....if it makes any difference at all. Thanks!