Methinks I can help you.. been where you are..
Okay, starting off, the life of bulbs totally varies. It varies based on how efficient your ballast is, how long you run your tubes, and how light-needy your livestock is.
If you are running VHO over a reef stocked with Anemones, Corals, etc, then you should replace your VHOs every 6-9 months. Many people lean towards fluorescent options because they "can't afford halide."
In the long run, halide is usually cheaper if set up carefully. Halides have a very high startup cost, and the bulbs are really expensive. However, you only have to replace halides every 12 months or so. My LFS runs theirs for 18 months, but livestock is never in their tanks for long, so I wouldn't recommend it. If you use big halides and run the right color temp (10,000K-20,000K), you don't need supplemental fluorescent for the animals. You might want them for you, but since your animals arent' dependant on them, you can replace them whenever you want and run as cheap of bulbs as you want (provided they don't cause algae blooms
).
To name an example, I was running (4) 110 watt VHO bulbs (2 10K, 2 20K) over my 55 reef. The bulbs are about 23 bucks each (plus shipping), replacing every 6 months. That comes out to 184 dollars per year in bulbs. I recently switched to halide, and am now running (2) 14,000K 175 watt halides over the same tank. My tank is overall doing much better, the lighting is much more attractive, and I my two bulbs are 80 bucks each. That comes out to 160 bucks a year in lighting. The other advantage is the all my VHOs were on one ballast, so if that ballast failed, I was screwed on lighting unitl I got it fixed. With two halides, I still have enough lighting to keep things alive if one ballast fails or one bulb goes out.
As for overdriving, the Icecap 440 and 660 will run NO bulbs at a much higher wattage than they are designed for. I use a 660 on my tank at work, a freshwater planted, which has 3 Sylvania daylight Home Depot Specials in it and one actinic VHO. All bulbs *look* the same brightness, and I have noticed no reduction in lamp life doing it this way. In a reef environment, however, you need to run "good for reef" bulbs. A NO Actinic bulb is only a few bucks less than a VHO, so you might as well go VHO.
Hate to say it, but lighting is THE most expensive part of a reef, and THE most important.
Good reading? Sure... The Conciencious Marine Aquarist by Bob Fenner has a whole chapter on lighting. I think his information is a little outdated though because he refers to halides as a sort of "new trend."
