Even as a passionate twenties-something engineer I would see my productivity and output fall off a cliff after 6-7 hours of work even if I had a lunch or tea/coffee break in the middle. I was fortunate to work for a lot of very cool bosses who essentially forced me out of office and occasionally gently teased me for working at night at home. I didn't realise how critical this was until I worked very briefly for another shop in the middle for a few weeks that demanded you finish everything within the same day to fit their scrum metrics. I could feel every ounce of energy sapped away after 6PM (after starting the day at 9AM) and had zero motivation to get anything done even though they demanded I stay. I was getting nothing done until they let us leave at post-10PM and I had basically spent hours staring at my screen. Left there as soon as I could

People miscount worked hours with the fervour that they miscount calorie intake!

Totally. I fall on this sometimes because I like my job. And it is still immediatelly clear that quality goes up if you work normal hours and exercise instead of 12 hour pulls

Keep up! These days the trend has changed. We have gone the other end now. "I work from 10am and start chilling out at 2pm and make much more money than before." (this is what they say, but not what they do)