you could start a data-collection initiative on the rate of successful calls of ditto-smeargle with 1hp, and on the rate of imposter dittos (since each imposter takes 1 less turn to faint), and then set up a program that will calculate the average number of pokemon KO'd for the number of recycles you have, as well as a handy graph showing the distribution of percentage likelihood for each number of possible pokemon. ;P
But in all serious, recycles probably could be used as an estimation of pokemon fainted. Note, however, that it is pokemon fainted, not turns, that matter, and since a regular ditto takes two turns to faint (1 to transform and 1 to faint), in ideal circumstances with a 100% call and 100% call success rate and no imposter dittos, it'd take 16, not 8, recycles (minus chain setup time) to get to forty KOs.
But in all serious, recycles probably could be used as an estimation of pokemon fainted. Note, however, that it is pokemon fainted, not turns, that matter, and since a regular ditto takes two turns to faint (1 to transform and 1 to faint), in ideal circumstances with a 100% call and 100% call success rate and no imposter dittos, it'd take 16, not 8, recycles (minus chain setup time) to get to forty KOs.