I've been searching for sheds for 32 years.Its been my experiene over the years that the majoriety of shedding occursafter march.That being said I generally start my search the day after deer season closes. Some years I find a bunch right out of the gate but more often than not in the early season I find bucks laying dead usually hit by cars.And sometimes just from old age or the rigors of the rut.
there was also a comment about the rats and squirrels eating them up.The tree rats have to find sheds just like we do so yes they do get a few,but they miss alot. I've found huge sheds that have laid in the elements for several years that werewhite and cracked but without a single gnaw mark on them.