After staying in a US university (specifically MIT) as a visiting scholar, a colleague of mine says that most of research labs are still working at midnight. I suspect that he is exaggerating. Don't Americans have life?
I know that there is no working hour limit for research, but based on my experience in UK, people used to leave following the official working hours.
Apart from exceptional cases, is it really common for research labs in the US university to work at night?
NOTE: I did not mean competition of early-stage researchers, I mean the common working styles. In any country, student might be in the library during the night (and similar in the lab). I meant does a US university professor expect to keep his lab active during the night? And does he visit the lab at night?