How many hours do you spend on gaming ?

Depends really. When I'm not laid off and housebound due to pandemics: probably 2x a week at maybe 4hrs an evening. Lately now that I'm stuck at home with nothing to do I'm probably at 8-10hrs a day, 4-5x a week. Don't watch much tv so there's not much else to do other than game right now.

15hrs a day seems a bit much. I'd worry about getting "cyber-sickness" (when you stare at a screen for long enough, consistently enough, that you develop this weird side effect of extreme nausea and even migraines any time you look at a screen). I had that back when I was working in graphic design 50hrs a week, and then spending all my free time watching netflix or on my phone. Sucks. For like a week any time I even looked at my PC screen or phone for more than 1 minute I'd have to go throw up and then deal with a major headache. Took like a week of absolutely no tv, phone, or computer before I readjusted and could ease my way back into it.