I thought the standard time was 6 months after the last Prolia shot. And some providers, such as Keith McCormick, suggest using the CTX (and maybe the P1NP) blood test to make sure the timing is right. According to McCormick's book "Great Bones" you need active bone remodeling for Reclast to work. (One of my docs says to just do the Reclast at 6 months and no need to rely on CTX). Another resource is Dr. Ben Leder's video on youtube entitled "Combinations and Sequencing."

Too early and too late with the Reclast are both possibly a problem. Do you have an endocrinologist and did they suggest a timing?