If the bulbs are run in series...and there's a short of any kind, even an intermittent one, as soon as any bulb of the circuit is cut out by the short, you have too much overall juice for the existing and "present" light rig...then boom, the first one goes, and after that it's popcorn time, tho not at that speed.
Are they blowing in the exact some order, every time ?
If so, your lights are more than likely rigged in series, and the problem will be with the SECOND one to blow, if it's an intermittent short (cause it'll blow when it comes back into the circuit, but not first, see?) or the FIRST one if no short of any kind is present.
A good idea would be continuity-checking your leads to those lights.
Just a thought, and don't take alla that as gospel, I've never worked on an MB5 before....but have seen similar issues on other bikes.