When will the seroma subside?

Seromas can be very annoying and can take a long time to resolve.  It's best to treat them right away.  Aspirations, or a placement of a new drain as soon as possible (within days, not tonight ;-) ) are the way to go.

Seromas can take time to resolve, Draining them is the best option as it will help control contour of the skin. You may require formal placement of a new drain. Stick with your plastic surgeon, he/she will get you through this brief period of difficulty. You will do well, Good luck Stephen M. Davis, MD, FACSGreen Hills Plastic Surgery

Drains usually come out when they are down to 20cc per day.  If yours were putting out 80cc, it is no surprise that you would have fluid collecting.  The drain needs to go back in, or the seroma can be drained by your surgeon.  Large weight loss patients have larger lymphatics, which explains why the seroma rate is much higher in weight loss patients (about thirty percent depending on the series).