I must still be missing something about the patterns of bitcoin generation in that first year. Why would the rate of mining success fall to roughly half of the first three months rate during the next six months?

If we look at an example of 10-20 minute intervals required to generate a block (there are 1440 minutes in a day), then it seems possible that 72 to 144 blocks could be generated in a day.

Thus if we use 90 days as a rough calculation of the first three months, then somewhere between 6480 to 12960 blocks would be generated in that first three months.

We know from Martti's first block sample in April that the block interval of 10 minutes was pretty much on track for the first three months - yet also indicates that there was at least someone running all the time.

If however, the rate of block generation over the next six months is more like 20 minutes on average (ie half the rate of the first three months), what is that due to?

- there wasn't at least one node working all the time
- the size of the block changed the solution rate
- something else?

Do we have any other examples like Martti's six month long sample that are identifiable?