Hi Traderman,
There are 210,240 blocks per year for four years, then that is cut in half, 105,120 for 4 years, then that is cut in half to 52560 for 4 years...etc, if you do that for 20 years the remainder becomes very small, that's where the estimate comes from .

Buratino:

As mining instruction implies BOINC project heavily utilizes CPU(s) and main memory resources, whereas GridCoin uses GPU(s) for mining. Is it indeed?

In this version, the AMD GPU does the mining and you are free to use AMD or Nvidia or CPU for boinc, and its total project utilization drives the subsidy.  In the version coming in the next 10 days, you can boinc projects that use the GPU (we found some that use the AMDs!) to gain more boinc credits, and the boinc credit trend over the lookback period helps drive the "shares" stored in the chain-- dont worry its similar in rewards, but more fair for heavy duty boinc users who want to take advantage of boinc using the GPUs.

Thanks everyone for the support-- we seem to be growing. 

Grid