I've never knew a WG working only 3 hours a day
. Usually, they stay until 12 midnight but some stay late until 3am-8am in the morning if they have an overnight appointments. I think locals here in HK are on a 12hrs work basis because they don't think about visa issues while Mainland/other WGs can work for a 24hrs basis due to they only have 2-3weeks visas so to maximize their time.