How long does it take to get burn-in when watching widescreen content on a CRT TV?

[damen]

On service calls I would see customers sets that were played several hours each day and I would see the burn in of the stock market reports that ran along the bottom, or the Weather Channel logo. During the first years of color TV, RCA cautioned leaving a color bar generator on too long. RCA said if burn in did occur, sometimes it could be "erased" by leaving the set running at high brightness with the vertical hold control set for a very fast roll.