Five seconds is a long time to be looking at another person, imo, unless you're trying to get somewhere with them: flirting, answering a tough question or demanding a response.
I've been (you'll laugh) timing my own looking at people. One or two seconds is about it. I look at every clerk who helps me until they make eye contact. I find I cannot stand to have someone help me who acts like an automaton and keeps their head ducked.
I don't make eye contact with every driver, just the ones who might hit me in intersections or who come close while turning.
I don't make eye contact with everyone who walks by (that would be exhausting). Interestingly, it was in the art museums where people seemed least likely to meet a friendly gaze or, if they met it, didn't respond. I felt like I was a painting that maybe wasn't quite up to snuff.