how long should video intro's be?

i think around 10 seconds to 20 is good. sometimes they are shorter. i made my intro a while back, it is way to long but im getting a new one.
so just keep it short in around 10-20 seconds.
I don't think this is the write thread but anyway what do i know haha :)

Am around 7-10 seconds :) if any longer it will get boring for the viewer and if any less it will look too short will have to be sped up and look unprofessional :)
:D Thank's for your help I really apreciate it! , I have decided to make my intro for my new series about 5 seconds long but I will be uploading the intro to my channel when finished so it would be sweet if you watched it and gave me some more feedback, thanks again
Long intros can kill a video's viewcount. Keep it short and simple, no more than a few seconds. A good idea is to open the video with a quick preview of what you are going to cover, then do your intro. You need to catch your viewers right away and give them a reason to watch your video.
Back in the days I had an intro from 1 minute xD. Now I have one that is 10 seconds and my new one (coming soon...) is only 4 seconds.
I find it difficult to view videos with a 10 seconds+ intro, I tend to lose interest very fast. I would recommend around the 5 seconds max.