Do I need to worry about pausing my Tivo causing image burn in on my plasma TV? I recently bought my first plasma (Panasonic 42" Viera 720p) and I understand burn-in is less a problem than it was on older plasmas. But we use the Pause feature on Tivo a lot! The Panny manual says not to display still images on the TV for "a long time"-- how long is a long time? 2 minutes, 15 minutes?