I had Botox done for my forehead lines. How long does this tightness and heaviness last?

Botox typically lasts 3 to 4 months, and so will the feeling of heaviness and tightness. Using Botox to help lift the brow might be helpful with the heaviness of the brow.

If you have never had Botox for forehead wrinkles then the stiff feeling that may occur is a new to you.Normally, you lift and furrow the forehead when you animate.  The object behind Botox is to soften these lines and calm down the wrinkling.  Hence, the muscles that produces these deep wrinkles are now less active. You should accommodate to this feeling in days to a week, afterwards you will enjoy a tension free appearance. 

Doing botox for forehead wrinkles can leave some patients unhappy because it does sometimes cause more heaviness of the brows (the muscles that elevate the brows are paralyzed by the botox and no longer function as they should).  As far as tightness, I am assuming that you are referring to your skin being more firm and less wrinkled, but I'm not as sure how to answer that question as I'm not entirely sure what you are referring to.  In most people, the duration of action of Botox is approximately 3 months, so you should start to notice some improvement in the heaviness by at least month 3 after injection.  I wouldn't necessarily give up on Botox injections for your forehead wrinkles, but it may need to be injected a little higher in your forehead to avoid the heaviness feeling.  Best of luck!