I am using the plain old stanard PFO ballasts (m59s???).
Joshua,
Actually JimD has been using a 400 watt XM for almost as long and has notice a change. So based on this we are now both really looking into the life span of these bulbs. Brian at Hellolights has no feedback yet on bulb life. I quest Jim and I are one of the first to use these bulbs. Jim is really more detailed at observing things than I, which is good because he has helped me many a times!!!! My thoughts, if the bulbs are really starting to go which is about 7 months, for me that is OK because I like the way may tank is with them and vs a radium setup the XMs IMO win hands down on preformance and cost.
Jim