OK, to add to the information bank, I've had Tinker (GWP) 3 full years now; she was one year when I got her. She came into season that first year about about a month after I got her home. The next two years, she showed nothing...not even moderate swelling. She turned four about two weeks ago and has just started full color. I've been looking just for general health purposes because I have no intention of breeding her. I'm too old and although she has some talent and great enthusiasm, she's not stellar enough to perpetuate her talents--maybe if I were younger, but probably not.
As FC and others have said, it's a crap shoot. Most females come in with some regularity; my first GWP was clock-like in her precision. If you're making plans on a littler, don't set anything in stone, your key player may become randomly freshening. I'm just relieved to see she is capable of coming into cycle--all things are connected and one issue may be a precursor of others to come.