I have a RP CRT and I was initially worried about burn-in on non 16x9 material. However, I have since set the contrast and brightness to sub 50% levels and have not worried about it since.
I watch mostly HD channels but even on the SD channels I am not concerned. The only time I get a little worried is during the weekends if the TV happens to be on for long periods of time on SD material.
I have not had a problem so far and I don't think I will.
Ordinarily he was insane, but he had lucid moments when he was merely stupid.