You'll know! It will start to illuminate more of an orange and less the white/orange glow! Haze has about the right time to change it! If it's a new bulb? Keep a record of how many hours are of use there is! Change at less than 20,000 hours. I'd say round 10,000. Conversion bulbs last less!

Ga Grown!
GaGrown Reviewed by GaGrown on . light hi all how long will a light last im use ing a son-t 400 w agro and how will i no if it past it use by date ? Rating: 5