They often range from ages 15-32, and sometimes over.
The term originates from a milk-tea cafe known as The Happy Lemon, which became ridiculously popular despite the rancid taste of their beverages. The cafe was packed full of hipsters, day in and day out, who lined up with friends to hog a table and chat about pretentious, material things.
Since, "A Happy Lemon" has become a general term for pretentious manila hipsters who, despite the situation of the country around them, continue to live their petty existences of pretentious get togethers and social gatherings. They usually are from the middle class or the upper class, condescending upon those of the lower or less fortunate class. The money in their wallets provides them with comfort and fuel for their egos, therefore they make it a point to show off how better they are and how much more money they have in comparison to others.
Person Two, seeing person one: "Oh my gosh did you see that girl? That cafe looks so hip, let's all go guys!"
Person Three, seeing person two: "It's the latest trend! Let's all go!"
Old Man: "Damn Happy Lemon Whippersnappers."