When joining same colored yarn

How much do I overlap the old and the new yarn?

I usually leave about 8 inches so I have enought to weave in if that is what I’m doing. There are other methods of joining if you’d like to check them out.

It says “same color” and “new color” for techniques, but technically any of them would be fine with the same color IMO.
http://www.knittinghelp.com/videos/knitting-tips