As a design or plan, Knols are not news items that are to be updated frequently. They are units of knowledge that do not change every day. But still on Knol platform, many information items can be posted. Knowledge keeps expanding and authors have to add additional content to their articles, essays, papers, and book chapters. Even research papers on Knol, can be updated and they can remain research projects under progress for all the time to come.
So the question Updating of Knols - Is It Happening? is pertinent. Presently there are around 600,000 knols and they are expanding at an approximate rate of 1000 new knols per day.
The Knols updated today search link provides an idea of old knols updated today.
3.7.2011 123 knols
100 knols per day would mean 365,000 knols per year. May be a good number.
Knol - 4927