How long would six sessions of Rejuvapen last?

Thanks for your question.  Rejuvapen is an excellent microneedling system, and your results will last a long time if you take excellent care of your skin.  It is not a bad idea to do maintenance treatment once or twice a year, but between treatments, you should use a good skin care regimen containing a retinoid, and strict sun protection with a zinc containing sunscreen.

Hello,
Microneedling treatments don't expire.  If you have a compliant skincare regimen that incorporates Vitamin A & C you are allowing your treatments to continue to work and last.  Microneedling is a collagen induced treatment that with a good at home regimen and drinking water and using SPF it will be a great treatment.  
Best wishes to you,