Do I need to replace my vlave stems with everynew tire?

[Gimpy]

So I finally bit the bullet and went in with a few friends on a tire changer.  I have a new tire on the way, so while I wait, I figured I would learn how to use the thing.  Getting the tire on and off seems to be pretty straight forward.  At least the videos seem to make it look easy enough.  But I have run across a few posts (not on here) that say you should change your valve stems.  Changing the valve stems isn't in any of the videos......

Is this something I need to do?  Does this apply to tubeless motorcycle tires? If it is needed, any advice? 

[Howie]

Common wisdom is you should, probably based on cars that get 40K plus on a set of tires and have rubber valve stems.  I don't change mine.

[ducpainter]

^^^^^

+1

metal stems are rarely replaced.

[DarkStaR]

I like 90* valve stems. 

[Speeddog]

I've not seen one on a Duc that legitimately needed replacing due to leakage.

I like 90* valve stems. 

+1.

[ducatiz]

the only time i change mine is the first time i do the tires and put on 90deg stems for older ones that didn't come with it.  other than that, no need.  the metal stem seals far better than the rubber ones ever will.

[Cloner]

Agreed.  The 90° stems are the business!  I often replace valve cores, but never metal stems.

[bikepilot]

I usually put in new rubber ones every change, but don't change metal ones unless they are crusty, leaking or otherwise disconcerting.

So far I've always used straight valve stems, they work fine for me.