[RichardN]

If you are reading music, or tabs or chord charts you can't look. If you don't do any of those things you still don't want your audience to be looking at the top of your head.

It's not unreasonable to be able to build your skill level to be able to find your way around the fretboard without looking.

However, we have all seen the best guitarists looking down occasionally or even often. And as mentioned previously, a particularly difficult passage may require a peek.