Bulb replacement

[rydr119]

I have a 250watt- 20K radium over my 65. When should I replace it? Its been up since March?

[silvers]

There is a new study that shows on most bulbs that they after 3mo. is the most sig. drop in PAR and color shift and looses very little until 18 to 24 mo. after 3mo its like 75% after18 mo. some where around 70% if in doubt buy a LUX meter and decide for yourself.

[kdblove_99]

I would think around 18 month range also. BUt if you ever notice a color change that is also a key to replace asap