I've used f.lux for more than 12 years now. My preference is 3700K after sunset, and 2600K during the last few hours before bedtime - rather warm color temperat

I've used f.lux for more than 12 years now. My preference is 3700K after sunset, and 2600K during the last few hours before bedtime - rather warm color temperatures - and it has definitely improved my ability to wind down before bedtime.