How long after a pannulectimy should you have pain in the abdonin from the drain tubes?

Not long. Today, most patient's having panniculectomy are treated with activated high-density platelets and do not require drains. In the rare cases needing such (due to bleeding difficulties, drains are typically removed in 2-5 days, with gradual natural closure of the remaining openings. Pain is relatively uncommon, and should be evaluated by your doctor to insure you are not having wound issues.
Unclear. Some describe pain- tho it's really tenderness- for as long as the drain is in. Pain with removal varies from none to minimal(most) to severe(the minority). I believe that, in the latter group, is has more to do with the emotional distress of picturing the event than actual pain- causing physical stimulus.
Drain Pain & Care. As long as there is no associated redness, pain from the drain tubes is often due to the stitch holding it in place. Any pressure on the tube will pull the stitch. Avoid pulling/tugging on the tube by securing it well. Gently cleanse the site with half strength peroxide followed by light application of triple antibiotic ointment to minimize pain and discomfort. First check with your md if this ok.
1-2 weeks. It is normal to have pain from the drain tubes while they are in place. Once removed, pain should go away in 1-2 weeks as it heals.
Abmdominoplasty Pain. Pain after panniculectomy or abdominoplasty can last a couple weeks or several months. Your surgeon should be able to evaluate if the pain you're having is normal healing or a problem. If there is a nerve that is healing slowly and tied up in scar tissue, it may take several months to resolve. This can be normal, but is pretty rare thankfully.