It seems that I quite often get a captcha confirmation when I post a question or answer. All it takes is to write a longish piece of text or check a couple of things to make sure what I am saying is on track. I can easily spend 15 to 20 minutes on an answer if I am being careful and thorough, especially if I paste in links to back up what I am saying.
This always makes me nervous, as well as being a pain/annoyance. What if the recaptcha site doesn't work properly? What if I lose my internet connection while doing it (happens a lot on my laptop due to a faulty wireless card)? What if I get the captcha wrong? It becomes easy to lose 15 - 30 minutes of work just because SO imposed an additional step on me.
Is this "too long" check really necessary? I mean, how long should it take a human to type 1000 characters of text? You can't really say, since it depends on the content. Certainly you can set a threshold of where it's too fast, but not where it's too slow.