Unfortunately, the answer is that each case varies somewhat. I made a post earlier in the thread by nervousbuyer on the subject.
It all depends on initial pricing with respect to comps. A less relevant factor is overall pricing as well. In the other post I was referring to communities in La Costa valley and some others in and around 4S Ranch. In these areas many sellers were coming in with initial pricings that were up to 10% above comps and had no reason being there. After about 40 days they were starting to come to church and bringing the pricing down.
Those were homes that were priced in the 900 and more range and had no reason being above say 850. One in particular came all the way down and has now received two offers in the past few days.
If they would have priced correctly to begin with they probably would have received higher offers to begin with.
So yeah your 45 day number is not a bad generalization. I would agree with you.