I have only had my minis for a short time, but...
My stallion was a yearling last spring and I needed/wanted to clip him. I just bought him, so couldn't wait til he shed out to see what was underneath.
My then 2 year old filly, was pretty much shed out when I brought her home in late April, a few long hairs on her jaw, but otherwise shed out.
My senior half-arab gelding is already shedding his long, white guard hairs. They are all over the place. The other horses are mostly sorrel, so their shedding isn't as noticeable with all the red cattle hair all over the place.