I've developed different red flags over the decades, and while I don't doubt you've encountered developers that are really slow, one of my red flags is the time

I've developed different red flags over the decades, and while I don't doubt you've encountered developers that are really slow, one of my red flags is the time estimate of "1-2 weeks". That's the off-the-cuff estimate that people give when they have no idea how long something will take. "A week or two" is "I can't imagine it would take very long, but my imagination isn't very good" ;)