How long is it supposed to it take for a benign tumor to grow?

It depends on what i: Benign tumors typically do not grow. But it depends on where it is located and what does your doctor think it is? A careful physical examination by your doctor is necessary to be sure that it is indeed benign as it is often difficult to tell the difference beween benign and malignant(this one grows in size as you watch it). I would be cautious and seek a second opinion and request an imaging test.