While you were a student you maintained status by taking 12 units every semester and not engaging in unauthorized employment. On OPT, you must also follow the following guidelines to maintain your student status:
Be aware that if you travel for long periods of time (more than 30 days) outside the US, or if you do not have a job offer when you attempt to re-enter the US, the port of entry officer at the airport may question your true intentions. It is within the power of the official at the port of entry to deny you admittance.
NOTE: It is your responsibility to keep your SEVIS record updated while in OPT status: The address you use on the OPT application form (I-765) will be temporarily entered in SEVIS for processing purposes. Once you receive the EAD (I-797D) from the USCIS, you must report your current address to the Office of International Services immediately. Again, you need to report any change of address within 10 days of that change.