Er, mine was run-in on the dyno, then thrashed to the redline, so possibly 3 miles total?
There are many differing views on the running in procedure, from none to a few hundred miles, and nobody can produce any evidence to prove their method was better than any other - that I've ever seen at least.
When I first fitted new pistons & rings I did three heat cycles before I took it out on the road, then treated it very gently for a good few hundred miles. But that was ten years ago, and nowadays I don't bother at all - the coatings on pistons, rings and cylinders is so hard there really isn't much bedding in to be done.
As for how far between rebuilds, it depends entirely on how many miles you do, and if you sieze it before you've worn anything out! Generally, what we're seeing is that seals dry out due to lack of use long before the bearings on the crank get goosed. I think I've read that in standard trim the engine shouldn't need any work for 20,000 miles or so, but I don't know anyone who kept their bike standard for that long to find out!