In most cases, drains come out within 1-2 weeks. Sometimes they have to stay in a bit longer. Each patient is different.
Most Plastic Surgeons use drains after a tummy tuck to remove the extra fluid that accumulates. Before they are removed, the drainage needs to be low enough for the body to absorb what is left behind. Most drains can be removed in one to two weeks but it can take longer (don't be too discouraged). Follow the recommendations of your surgeon and you should do well.