I've used XM10,000K's in 175 electronic and 400w magnetic ballasts. Both nice, very strong and white but need actinic supplementation. Easy year on them.
On frag tanks and fuge I've used 400w Iwasaki 6500K bulbs. Those are some high output bulbs but not any touch of blue to the viewing color. On spectral measurements it's there and even stronger than many of the blue bulbs but there is such a large output in all the other spectrums it has a yellow appearance even w/vho's. A big plus to these is they have very little loss of output measurements even at the 2 year mark.
In 175w bulbs there is a 15,000K Iwasaki bulb which puts out intense par that is higher than all but a few 250 watt bulbs and those are in the 10,000k range. That's in comparison to standard 250's. I'm not sure if these Iwasaki's will last as long as the traditional 6500K Iwasaki's but with thier history, I'd bet they at least get close.
I've tried XM15000K bulbs in the 175 level. They have a great color but the output of a flashlight with weak batteries. They would be great on a softy tank I would imagine.
Most bulbs are good for a year with the exception of Radiums which need changed at 6 months. And the Iwasaki's for a couple years. Another thing that shortens bulb life is running non-hqi rated bulbs on hqi ballasts although many do and still make them go a year but they probably should be on a slightly shorter interval.
