Hi and thank you for asking this question. We all know 60's are the new 50's and to answer your question, you are not at all too old for treatments of Sculptra Therapy!
With the experience you have of the past year, it is evident you have started to see results, however very possible (likely) that you have not yet had enough product to see a more impressive production of collagen and ample volume restoration. Without photos or seeing you in person, I am of the belief you should have a 3rd session of Sculptra, and in that 3rd session, have 2 vials of product. 6 vials is a very common therapy recommendation.
We very commonly see patients for 3 sessions, providing 2 vials at each session, scheduled at 6 week intervals. This allows patients to start seeing the results (usually noticable a few weeks following the 2nd treatment), and results are most appreciated soon after the 3rd treatment. Your body has had time to produce enough collagen at that point and the overall volume and visible changes are well on their way. It will continue to work weeks following the 3rd session.
You've started to see what Sculptra will do for you, I believe another session is beneficial.
I hope this is helpful and encouraging feedback to your question.