A small study shows crunch time makes developers less effective

I think anyone who's gone through and completed an intensive collegiate CS program can strongly attest to this.

I can also relate this research to quality / seemingly-well-meaning managers I've had over the past few years. Managers who seem in control never pass off the stress of deadlines or crunch to engineers - longer time thinking about things regardless of difficulty result in better code and fewer potential land-mines down the road (even in startups). As soon as you deviate from that or start putting the pressure on engineers to crunch for a deadline you're asking for high-turnover and bad code that WILL cause issues down the line (many engineers also see this as a direct attack on their ability to uphold their quality of work).

I've been harping on this with evidence from other industries gathered by Evan Robinson (http://www.igda.org/?page=crunchsixlessons), but nice to see direct post-facto evidence from software teams.

Some more reasons why longer hours make you less effective: https://codewithoutrules.com/2018/02/11/working-long-hours/