Parents bought me a 180W fluorescent (therefore 10800 to 18000 Lumens according to https://en.wikipedia.org/wiki/Luminous_efficacy#Examples_2 ) anti-SAD lamp.
Stupidly, I used it as an evening lamp instead of anti-SAD. I had serious troubles getting to sleep for an entire year. Typically took 1-3 hours. Blamed coffee, stress, etc. Got blackout curtains, earplugs, cooled room temp, reduced coffee, etc. When I made the connection b/t falling asleep and the anti-SAD lamp, I stopped using it altogether and almost instantly started falling asleep rapidly.
So I conclude my 10k-18k lumen lamp stimulated my awake cycle by about 1-3 hours. My suggestion therefore is: use the lamp at either end of the day in winter: just before sunrise and just after sunset. And certainly to shut it off 3 hours before bedtime. In practice this is tricky because the "unwanted dark hours" are 4:30pm to 7:30pm which is: at work, my commute home and first hour at home. So I need three lights, including one in the car?!