I guess my car is an anomaly. I've had it over 8 months now and no burned out headlamps. Not sure what's in there. I do have DRL enabled but never have my headlight switch to the ON position when starting or stopping the engine. I know some here have said they leave their headlight switch on all the time. Each lamp has an expected lifetime, if you're running your headlamps at full power all the time the car is running then they will last the least amount. DRL will run at partial power which probably allows them to last somewhat longer than on full. DRL disabled will create the greatest lamp lifespan. From what I've seen the "heavy duty" H7's will last around 900 hours. If you drive 10 hours per week that's 90 weeks, just under 2 years. Life expentancy for lamps seems to shorten the more they're turned on and off (from what I understand).
An off topic, sort of: I have a ham radio in my car. I can remember years ago an instruction manual for one of the radio's I had said to not keep the radio on while starting the engine because a voltage spike may occur. For that reason I always have the radio off when starting the engine and have had no problems so far. Likewise, I keep the headlight switch in the OFF position when starting my car and if the parking brake is not engaged the DRL circuit will light the lamps after the engine starts, thus theoretically avoiding any spike that may occur.
I'm not saying it happens with every car but several folks have said they do not leave their headlight switch ON until after starting their car and thus have had long headlamp life. It would be nice if that was the solution to all of our problems. Yes, another solution seems to be installing HID's and that would be nice (for $200 or so it isn't all that bad). From what I've read over time and many threads this seems to be the summary.
I'm not a rocket scientist or brain surgeon so don't take this as gospel. I could be totally wrong as to why the lamps don't last long. Silverstars seem to last the shortest, for whatever reason, but are pretty good in most other vehicles. I can't explain that. Anyway, I hope this helps.
Dave