Sorry, I may have misunderstood your question?, If your agapanthus is a new plant it may take 3 - 4 years to first come into flower and will then flower every year. Is it in a pot or in the ground? They usually flower quicker in the pot when their roots are restricted. Hope this helps. I am only going on what happens to my agapanthus.
It was flowering when I bought it late summer last year and I have planted it in a pot. I am being just inpatient wanting to know when the long flowering stems start to appear. ;o)