I realized that my previous analysis was missing a key bit of information, namely how many long-standing R01s from previous years failed to make it to the present. I examined R01s in years 40+ from FY2010. There were 47 grants awarded to 47 distinct PIs. Of these grants, 24 do not appear as active, funded awards at present. Thus, approximately 50% of the R01s in years 40+ in FY2010 are still funded at present and 50% are not.
Of the PIs corresponding to the 24 year 40+ R01 grants that are no longer funded, 9 still have other NIH funding at present. In most cases, these are other long-standing (but less than year 40) grants while in a few cases they appear to be new projects.