I also use the Arcadia 160w bulbs. I have two which have been running every day (apart from 10 days) for around 32 months and 28 months respectively. They were still producing good levels of UVB at the last test four months ago - see here
http://www.shelledwarriors.co.uk/for...0&postcount=96
Bulbs will blow for various reasons, moisture getting on the bulb from a spray or the bulb not getting a good connection with the contact in the holder, lack of a surge protector and just a duff bulb. The good thing about the Arcadia is that you get a 12 month no quibble guarantee. Megaray used to be 6 months. I have had duff Megarays in the past as well as duff Solarglo