To answer the original (inferred) question: No, unplugging one of your headlights will not cause the other to burn out (much) quicker. The reason that the second headlight seems to burn out right after the first one is because they have the exact same runtime on them. The filament material of an incandescent bulb (even one surrounded by halogen gas) has a finite and predictable number of lumen-hours when new.
Since both of your headlights receive the same exact applied voltage for the same exact amount of time they will have very similar lives.
The idea that the increased voltage on the second bulb (after the first one burns open) will hasten its demise is true, but to a relatively insignificant extent. The difference in applied voltage will occur due to the reduced current draw of only one headlight in parallel, which will result in less voltage drop on the distributed resistances of the wiring harness. So, just throwing out some numbers here, if your charging system is healthy and putting out 14.2V, with both headlights running you may be getting 13.6V to the bulbs with both headlights running and it may go up to 13.8V when the first one burned out. In other words the lamps power will be boosted by a bit less than 1.5%, and the lifespan of that bulb will be hastened by that same amount. Hardly something to worry about.
35 watt HIDs consume more than 35 watts each due to losses in the ignitor/ballast to generate the high voltage needed for the Xenon gas discharge. Using them will save you a few watts over the 50/55W halogens, but it is hardly worth doing that for that reason. The reason I have them installed is because it makes you stand out more in the daylight, and gives more light down the road at night. It also takes the entire load current of the headlights off of the ignition switch, which (as all 2nd gen owners know) is a good idea.
On my power starved 1st Gen FJR (w/ HID headlights) I've found that I can run two 90 watt jacket liners (nominally being pulsed at ~50% duty cycle) and two pairs of heated gloves along with all of the other normally found rider electronica (intercom system, GPS, radar detector, cell phones a-chargin', etc.) and still maintain an adequate battery charging voltage. Of course I do have a Datel panel voltmeter to keep an eye on that. But for your second gen the load you propose should be a breeze.
