I just can't stand any king of after-market stuff on my classic cars. My cars aren't show cars, but one of the things I don't like seeing when I walk through a car show is a real nice classic car (or truck) with something wired into or installed on the car that shouldn't be there. MCA allows certain things on the cars when they judge them from what I hear, but I still think a classic or antique should be left the way it was originally. Halogen headlights are one of those things that are probably easier to find than standard headlight bulbs, with the exception of reproductions of the originals.
If you aren't sure about the high beam switch, replace it. Make sure that the wiring at the switch is clean and free from fust as a dirty connection (or a connection that isn't good) causes heat build up and more current draw. The high beam switch is on the floor where dirt, grime and rusty floors are common.
If your car still has the original headlight switch, replace it too. When you unplug the connector from the headlight switch inspect it to be sure the ends of the wires don't show signs of overheating (melting of the insulation on the wiring or severely discolored insulation near the connector).
I actually had a bad ORIGINAL serviceable voltage regulator on the 1966 289 Coupe that I bought for my daughter several years ago. I was running the halogens with the regulator stuck and when I was driving the headlights and/or high beams were super bright and when I would come to a stop sign or traffic light the lights would get very dim. I didn't ever have the headlight switch flash off even with that problem. Oh, yes, the original voltage regulator wasn't something I was able to fix though. I fixed that a while back by replacing the regulator.
(edit) If people wouldn't over-drive their headlights or high beams the original headlights should be sufficient to light the roadway in front of a car. I agree that halogens are brighter, but the speed limit is the speed limit, and humans aren't moles, owls or cats and weren't really designed for seeing too well into the darkness. For every mile per hour you drive faster at night you reduce the amount of roadway you can see at night and you also reduce your reaction time to hazards in the dark on the road in front of you. (end edit)