Personally, I spend 98% of my time in Linux, but I dual-boot just for the sake of the few games I like that need Windows to run. If not for that, I'd have dropped Windows years ago.
I haven't logged my hours, but substitute 98% above with whatever my number is (90+%). I don't even have Windows installed on my main, but older, desktop. I just have it on my newer laptop, which is where I do any gaming of significance (when I have time nowadays).
Personally, I spend 98% of my time in Linux, but I dual-boot just for the sake of the few games I like that need Windows to run. If not for that, I'd have dropped Windows years ago.