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If you know now that you will optimize 30 pages then make your plan now. Determine which pages will focus which key words or phrases. This will help you avoid cannibalization within your own site. You can also start now with building anchor links between each page as you optimize them. As you build links or otherwise improve your first few pages, you may encounter an opportunity for another page. You can then either take notes so you can easily backtrack later, or you can stretch and include the extra page while it is convenient. An example is you may have a site which sells insurance. You might contact an auto dealer and obtain a link on their site referring car buyers to your site. At the same time perhaps you might think about the health or life insurance needs of the car dealer's employees and find an opportunity there as well. One last thought. Once you feel your first 5 pages are optimized, I would not recommend waiting for them to rank well. Go ahead and jump into the next 5. It takes time for SEO to work. There is no benefit to waiting. Get started now.

I am fairly sure that Pagerank is now constantly updated, it may well be that they only adjust the visible pagerank every three months though. I can only say this next bit speculatively because I don't have the data (I would love to see the periods and numbers for the site above), but the cap itself might be a somewhat fluid idea, pages may be retained in the index as they are discovered but get pared back to their "hard cap" periodically.