Is there a number of Rejuvapen treatments that are recommended? Can you do too many?

The micro injuries created by Rejuvapen naturally stimulate the production of collagen and elastin. This creates healthier and tighter-looking skin and improves the appearance of fine lines , wrinkles , pores, and acne scars .The skin will continue to build collagen for up to six months. Patients will typically receive a series of 3 treatments 1 month apart for aging and then maintain with additional treatment 3-6 times per year for continued improvement.

When dealing with acne scars or stretch marks the initial series would start at 6 and could take as many as 10-12 depending on the severity of the scars/stretch marks.

The number of treatments depends on skin damage, type, thinness,  and aggressiveness of each treatment. 

The Rejuvapen is one of several microneedling devices.  This is one of several excellent in-office microneedling instruments that provide collagen induction therapy for areas of skin scars, reducing pore size and stretch marks. Work with your cosmetic dermatologist to determine how many treatments will be appropriate for your treatment goals and skin type.
I hope this is helpful to you.
Steve Greene MD