I dont think there is any set time at all, as Winter said remove it when you are comfortable, I still have ours in DD's bed and she is 2.5yrs, I dont think I am paranoid it just feels good to have a little peice of mind and also be able to hear her at night as she still wakes most nights, do what you feel happy with, and yeah if its going off all the time I would contact the company and ask them for advice, tell them you have done what it recomends and are still having issues with it going off1

good luck