The only research on the topic is from Bernestain, 2006
"The study showed that for the first two days, pulling on a hair always resulted in a lost graft, but the chance of the graft being removed started to decrease by the third day. By the sixth day pulling on a hair would no longer dislodge the graft. Pulling on an adherent scab always resulted in a lost graft through day five, with the incidence decreasing through day eight. However, by nine days post-op, grafts were no longer at risk of being dislodged."
After 3 days, excpet you do not try to stretch your hair out, you are perfectly sage.
After 5 days, you won't dislodge the graft even if you try to pull out your hair.