I have mine set to 4 minutes because I do a lot of ebook reading so, if I'm reading in public and get distracted mid-page by something, 4 minutes is usually long enough so that I can get back to reading and get to the next page-turn before the autolock kicks in.
I could probably get away with 2 minutes in the winter but, in the city in the summer time, I find that there is more to distract me so the higher timeout is frequently useful 🙂.
- Julian