Stupid Panny V10 question

[Maggot]

I've had my Panny V10-50 inch about 2 months now and love it. I guess I've watched about 50 hours, so I'm about half way there to the 100 hour burn in mark I keep hearing about. I purchased 4:3 films like The Wizard of Oz and Gone with the Wind a while back, but except for a brief look see, I have not watched them. I just purchased Star Trek(the original series) season 1 and popped it in. Wow! Anyhow, I want to be sure I'm doing things right. When I play the disc it normally puts black bars on the sides for 4:3, but there's another mode that puts grey bars instead. Which one should I be using? Also, because I'm worried, I've been watching Star Trek in the "Just" mode, which is like "Full", but a little better. But again, which mode it best for 4:3, the normal black bars OR the grey ones. Should I stick with an expanded image until about 100 hours for 4:3? Also, how often do you use the side scrolling image retention bars and for how long. Thanks.