Day length primarily governs the breeding cycle, not necessarily the weather. We are getting some leaf growth already, but the weather can change, (note the snow today) which will slow things down.
I've always had better luck with just a single hen or no decoy at all during the late seasons. For one thing, leafout closes in the open areas so that many times the birds are in range by the time they should be seeing something, and, by that time, they've been 2-hens-and-jake'ed to the point of avoiding tom decoys.