How long is long in overbought territory?

Just wanted to share a quick example of what Chris means when he says that we should remember that the market can stay overbought for long periods of time, but generally stays oversold for a short period of time. Here's a comparison between the NYSE BPI and NYSE over 15-16 months. You can see the period of Jan through Feb 07 as well as Apr through June 07 and how long they stayed overbought, 2 months and 3 months respectively. I remember asking myself a few times in the course, how long is long? Now I know and so do you.