I have a Fluke ScopeMeter 97 that's come in really handy over the years. Before I got it, it was a sales rep's demo unit, so it was used pretty hard. The screen backlight is an electroluminescent panel, and their intensity can fall off pretty dramatically over it's life. This particular display is also transflective, which makes it extremely readable under direct sunlight, but means the backlight is essential to using it in indoor lighting. To use it in the past, I'd shine a bright desk light on it, but I've always wished the backlight would just work.
I have a pair of Acer LCD monitors that I have used since 2006. They were super-cheap when I bought them, but have worked well enough over the years. Some time last year, one of the monitors started having dark lines skittering through the image the entire time it was on. Knowing that it was over 6 years old, I figured one of the backlight tubes was dying and I finally decided to take it apart.