Headlight Bulb Blown, Do You Replace Both?

[davesimmo]

I have had a headlight bulb go and they have been in for 2/3 years. Would you replace both sides or just the one that's blown.
Someone told me that they loose brightness so should do the pair. Is this true??
Thanks guys.

 

[Murton]

I normally just replace the side which has blown and don't notice that the new one is any brighter.
Have a look at the one the other side though. If it looks quite black then its probably on its way out anyway so might be easier replacing it at the same time.