I run in a young, professional circle where people have high income, high stress jobs working for multinationals. China is apparently still a hardship posting for these folks and they've been compensating by partying way too hard. I either need to stop bucking to peer pressure or find new friends because I find myself drinking rather heavily lately, if only to keep up appearances.
I think they imbibe a lot more than many of you guys, who are older (but still young at heart, don't worry), more experienced, have settled down here for good. Many of you have family lives including spouses and children and I'm still at the age where most people in my peer group are dissatisfied if they fucked less than 3 girls that weekend. Certainly, being younger and more reckless tends to lead to more drunken benders than if you have a wife and kids to go home to.
I'm not trying to be judgmental mind you, but I may have spoken in haste and overgeneralized. Certainly not all expats party too hard all the time but it's certainly a part of the landscape in the Middle Kingdom.