? about MH lights

When a MH light is no good any more does it just burn out or does it still work and just start loosing lumens.thanx for any help

MH, like all other HID lighting, loses lumens from the very first time you strike it. After 6 months of use, it has dimmed to the point where it needs to be replaced. Other HID lamps may have longer replacement intervals but they all do the same thing.

Get 315W CMH lights if you want a good HID for growing, or go with COB LED as it's coming down in price rapidly.