t,
As the crowns mature, each year more and more buds are formed on the crown not to mention the additional buds that will form on any rhizomes that grow out from the crown. The buds just emerge at different times. After about 5 years of growing, I realized that the time frame between the first to shoot up and the stragglers was about 3 months. At that point I realized that knocking down the first flush of growth would buy me a couple weeks to get other 'green' things done (anyone who works with plants realizes that time is at a 'premium' in the spring). Once I felt confident about the whole scenario it's become a regular cultural practice in my little garden. Kinda scary at first but if the big growers do it you gotta believe we can get away with it. Good luck.
Forgot to mention that the number of buds that will sprout is pretty much fixed as far as I know. I don't think that removing the first growth will promote 'more' buds to emerge. The amount of harvest is up in the air as I've been doing it this way for about 20 yrs now. I usually just whack back to about 5-6 per pole for the weak varieties and no more than about 4 for the Cascades and Chinooks(they do the best for me and have the longest sidearms).