"Disable when using" should have a change delay
"Disable when using" should have a delay when switch away momentarily from the application set for disable.
For example, Photoshop. If set to disable, works great. But if you alt-tab to check on a file in Windows Explorer, f.lux starts changing temperature. Alt-tab back to Photoshop, changes again. That generates a headache for me rather quickly.
So some of delay is desirable. Or instead of attempting to be "smart", simply trigger "disable for 1 hour" upon what f.lux thinks is an app exit/switch-away.
We do have kind of a complicated state model that considers how long it's been disabled, but we can always do better.