What is a good length for medium hair style (for men)?

I'm growing mine so I am just wondering.What is a good length for medium hair style (for men)?
My favorite mens hair style:



http://smashingstyles.com/uploads/2008/1



http://z.about.com/d/menshair/1/0/T/-/-/



http://markthebarber.co.uk/hairstyles.jp