[mmanfrin]

Sous vide needs way more than 20 minutes, but you are correct that once it's reached the target internal temp, the time doesn't much matter (beyond going too far).

Typically, about 90 minutes is a good spot for almost all temps with steak, a little more if it's a thick steak.

[menage]

For tender cuts of meat (like a good steak) it might be true that temperature is what matters. But cooking sous vide for 12-24 hours can turn a tough cut into incredibly tender juicy meat - the connective tissue needs time as well as temperature to break down.

[Scaevolus]

It's quadratic. You need four times longer for a steak that's twice as thick.

[dzhiurgis]

I've certainly overcooked more than a few steaks due to cooking too long, not too hot. Also, it seems it sometimes depends on meat quality (not just the cut). Or maybe it was the sear that I tend to overdo.