But falk the whole point of the OEM relay is too keep the current from the headlights off the switch circuit. The only thing the switch is actually powering is the coil inside the relay. The current and voltage on the switched circuit does not at all affect the switch. The switch is completely isolated from the headlight circuit, what your saying can only damage the OEM relay, if it even would, I don't think it would. And falk when you have a relay or anything that can take say 25A and say it sees a million fraction of a second bursts of 10A, that won't hurt it. It doesn't add up, unless there is enough current to heat up the relay. 10a or 5a for a fraction of a second isn't enough heat to damage the relay even over a very long period of time. Now if say the ignition took 40amps, and you were running it on a 25A relay, it would be fine at first, but over time that over amperage would damage the relay. I wouldn't be at all concerned with running your HIDs on the stock circuit, unless you were running high powered HIDs. But there is always an advantage to having the circuit external and accessible.

EDIT: CJDM that would not affect your bulb going out.

 

I'd say the draw is less than 5A at 12v. I have 5A fuses in my relay harness and they never blow, both when the battery is throwing 14.5V and 12V out.

 

A 5a fuse will only blow if 5a is held for a about a second or a little more. The ignition doesn't stay on long enough to blow the fuse.

EDIT: The fuses usually come with information on how long the fuse takes to blow at what amperage. They usually take a second to blow at their rated value, remember the fuse has to get hot before it can blow.