oh my enrolment took a little over 2 hours.... just know what subjects you are enrolling into and have your planned timetable. oh and if you don't get the times you want, don't stress over it. you can change it right afterwards online. when i was getting my timetable done, i just told the guy to register me in any times.
oh and sorry to be the bearer of bad news. but i remember reading somewhere that if you are enrolling, they won't let you enrol in a time earlier than what is allocated for your name. you will be allowed to enrol at a LATER time after all the enrolments are out of the way.