I am in a similar position as OP. I do 15-20 hours of work and watch Twitch or YouTube the rest of the time. I am a lead dev at a startup and developed one of their main products. I have always implemented every feature in a few days or less. Bug fixes usually take 30-45 minutes. Meanwhile another lead dev, who handles the development of another product, takes at least 2 days to fix a simple bug, and 1-2 weeks to implement a simple feature.

Personally I don't see why I should be overworked if I get all of my stuff done in a short amount of time. Plus because I feel guilty I am always available on Slack and answer or even code on demand if somebody really needs it.

I sense that higher ups look at me as a hard worker and a good employee, but if only they knew the thruth. But if I was forced to work a lot more I would probably quit.