I replace mine every nine to twelve months. The link shows a nice comparision of the different types of bulbs.
http://www.reefcentral.com/library/pc_comparison.html
I have had rotten luck purchasing lights mail order. Sure the prices are better, and the vendor has always righted the situation, but for me it is not worth the headache. There are few things worse than unpacking an item broken in transit, (whatever it may be).
I bought one of these units in August. It arrived as advertised. I found several positive reviews of the company, (PFO, they also have their own website). I think he overcharges for shipping, ($35.00) but for me it was a good deal.
