I think like the other commentator noted, I don't do this blindly, as I also wouldn't if I was instructing a junior engineer. I have a rough sense of how long it would take me to research all angles of the task. 5 minutes for a complicated feature is too short for a comprehensive plan. Letting it run for a few hours is also probably unproductive. But 10-60 minutes depending on complexity with followup review is a nice sweet spot. Just my $0.02.