Is it recommended to wear a girdle / compression garment when doing weight lifting or ab work outs 8 weeks after tummy tuck?

Most plastic surgeons have their tummy tuck patients wear some sort of compression garment after surgery.  I prefer the soft, elastic variety with plenty of cushion.  I usually have my patients wear a garment for a minimum of six weeks.  I think it helps with swelling, the prevention of seromas, and provides added support while the deeper, fascial layers continue to heal.  If a patient develops a persistent seroma, I might make them wear the garment even longer.  At eight weeks, it is unlikely that the garment is providing any real protective function.  Of course, it probably does not cause any harm, and many patients just feel more comfortable with the garment on, at least when they first initiate exercise. 

Only your doctor knows the answer for your
specific situation. For my own patients, depending on the exact procedure they
had, 8 weeks is typically when there are no longer any restrictions for
activity.

Typical garments are worn for 6 weeks after surgery. It is not unusual to wear them longer and during vigorous physical activity.  Follow the advice of your plastic surgeon.

I recommend wearing the binder for 6 weeks afterward, so as long as your plastic surgeon is okay with this you should be able to leave it off while starting out slowly lifting weights.

Surgeons will have different opinions and advise regarding the use of garments as well as when to return to exercise. it would be best to simply check in with your surgeon's office.

is required in my patients for only 6 weeks... and then they start resuming activities slowly getting back to their normal routine.  If they want to wear the garment longer, it certainly does not harm anything.

Wearing a supportive garment can never hurt.  My concern would be with strenuous abdominal activities, particularly weight lifting two months after surgery.  This should be discussed with your plastic surgeon and, of course, would certainly depend upon the weights involved.

Consult with your plastic surgeon. Common sense prevails. If it hurts, don't do it. Go slowly as it may be very sore the following day. A compression garment may help support your abdominal musculature.

Wearing the garment aids in the healing process and helps in reducing the bruising and tissue swelling. Being 8 weeks out already, I think the advantage of wearing it will be limited.