I often hear this question in the USA.
It is true the bulbs burn at least one or two years.
BUT: The spectrum changes after about 6-8 months. To have a stable spectrum, the bulbs should be changed after this time
Ahh thanks for your reply, whatever your doing it looks awesome.
Thanks for posting your Parms. looks like you have it Nailed!
I look forward to your input here @ RF, hope you stay around & show us some things we could learn from. I knew there was a guestimated 20 to 25% shift but didn't think it was that quick.