You are talking about a very common issue in plastic surgery.
Anatomically, as the eye lids and eyebrows sag, your brain sends signals to lift the excess skin and weight off of the eyelids. One way to do this is to lift the forehead, sometimes imperceptibly. However, after the excess eyelid skin is removed, the brain stops sending the message and the eyebrow/forehead falls. Thus, 6 weeks after an eyelid lift, you look saggy again.
The proper way to treat this problem is with diagnosis from the outset. But in your case, a browlift at this time sounds appropriate.
How would you know if you need a browlift? I tell my patients to close there eyes for a couple of minutes, this relaxes the forehead muscles. Then put your finger on the eyebrow and open your eyes. If the eyebrow tries to lift up without conscious effort, then a browlift is warranted.