They can and do drop any where from early Jan. to early April.
I think the timing has a lot to do with how active a particular Buck was in the Rut breeding Does. More breeding and his testosterone drops quicker thus he will shed his antlers quicker.
I also think rougher weather can cause Bucks to drop earlier for the same reasons.
Like I said I've seen a few 1 1/2 year old bucks still carrying their little racks the 1st of April
Dan