I only have one season (and one resulting clutch) under my belt, but I started pairing in October of last year... didn't get any eggs until mid-June, so I don't know if it mattered! I guess they go when they want to, regardless of when you start introducing mates.
Same thing happen to me too... started pairing two pairs in Oct.. one laid in March and another in July 1st... next week is the second clutch hatching time...