How many times does a seroma need to be drained before it goes away?

Seromas are not uncommon after a hematoma has been removed.  The seroma fluid usually needs to be removed several times, and each time there is less fluid.  If it doesn't seem to be resolving, a drain can be put in for a few days.  It will eventually go away and you will heal normally. 

It sounds like your surgeon is taking care of it. Although seromas are rare, they typically resolve in the face/cheek without any impact on the results of your procedure. It is a nuisance and can prolong the recovery. With close follow up, reassurance, and periodic aspiration by your surgeon, it should not have any lasting effect.