This is a well known problem.
Mainly caused by using small gauge wire and not having a relay in the circuit.
The bulb ends up with about 10V instead of 12V.
It is pretty easy to install a relay and larger wires.
The trick is using a DPDT relay, and you should wire it so that the DRL still work, and then the relay is activated when you turn on your headlights.
Search this sight for headlight fix, and there is a post I made on how to do this, plus a lot of other posts.
This post contains schematics:
Bounder headlight fix
Regards,
Dan