I start OB right away at 8 weeks - but for the first 2-4 months its small marker training sessions teaching games that will later become commands (through, weave, spin, go out/come in etc). By 8-9 months I was proofing my female, was more like 13-14 months with my male, just different times with completely understanding concepts and I don't proof until I know they understand 100%.
I have never had a problem with not enough "crazy". I just can't imagine how much "crazy" I would have if I didn't start young...
I do my own tug work with posting for the first 8-9 months, while also putting the pup in front of the helper once/twice a week for fun play sessions.
I start tracking at 8 weeks as well, just short scent pads, circle tracks and food searches. Progressing to straight tracks then corners, when the dog is ready (no set age), then once they can do a 500 pace track with at least 4 corners and only food drops, I progress to articles. I start articles off the track marker training a "show me" with a down at the article.
I also taught agility starting 8 weeks, freestyle, Rally-O and Kayaking. I start from day one teaching my dogs small increments of EVERYTHING I am going to need later on, and just do some imprinting in each area making it fun for the dog.