[bobH]

I did DOT 5 in my 51-yr-old pickup, about in the 1980's. It (DOT5) has been ok, and especially ok, as my old pickup sits out in the weather. I opened up the system about 15 years ago, basically for service and to see what all the parts looked like. Everything still looked clean and pristine. So... It's been ok. But, at this stage of my life, I'd never bother with it again. The DOT 3 and 4 suggestions are what I've followed in all recent years. I, for one, am not messing with 5 again.
edit... I should have added, on my DOT3/4 cars, I flush the system, every few years, based on accumulated moisture. I have done yearly flushes, which seems to be more often than necessary. Then I switched to flushing every two or three years, and that seems to be ok. A primary interest for me, on modern cars, is to keep all the abs stuff in good working order.