How long can I keep my metal halides?

[xabxam]

I have had my 2 Ushio 150 metal halide bulbs over my 75 gal tank for 11 months.How much longer should I use them before I change the bulbs?

 

[xabxam]

bump

 

[brinkdrum]

I believe most people recommend changing halides once every 12-14 months. Although i've heard they can be effective up to a year and a half. What does everyone else think?

 

[zanemoseley]

Some bulbs like Radiums are only good for about 6-8months, I've heard XM's are good from 8-12 months. I wouldn't run a bulb more than a year under normal usage.

 

[xabxam]

How long can USHIO bulbs be used for?