I once heard that a certain figure (I believe the GR"A but may be mistaken) made sure to redeem his son from different Kohanim upon meeting them at different junctures in his life. The idea being that since we are uncertain about the lineage of Kohanim today, he would be improving his chances of fulfilling the miswah at least once with a definite Kohen.
A) Does anyone know the source of this story? I of course welcome any related information (e.g. sources that commend or even prescribe such a practice).
B) Were one to proceed as such, would a new blessing be required each time?
This Q concerns a different but related scenario asked about here.