Not me. If I calibrate for game X, reboot, and then play game X again, no need to reboot.
However, if I then play a different game Y, I often need to recalibrate reboot or no.
I'm talking both the PC gun and the TV gun.
A question I have no idea if it matters or not:
Is power still going to your motherboard? ATX motherboards always have power, even when turned off, and maybe the gun box needs a trickle through the USB port to save the savings?