I can personally vouch for this myself in practice.

This is a classic case of quality vs quantity. Depending on my workload, I have sessions of varying time of hyper-activity. If something is highly urgent, then these sessions can endure for as long as I need. The only thing I require is that I'm not that tired.

Luckily, I work in an environment that only requires results. Time is of course tracked, but the ultimate reflection of my value is in my creative thinking and the actual work that gets done.