I wouldn't worry about it, Rodinal or RO9 are essintialy the same, they will keep forever, they might go black, might thicken up over many years to an almost treacle like consistansy but they will still develop film as well as ever, I have used Rodinal out of a glass bottle that must have been 30 or maybe 40 years old, just the dregs, that I found at the back of the chemical cuboard as I had run out of Rodinal and wanted to get a film developed, and it was good as fresh, To answer your question, there is bound to be slight differences, and I would not chance it, just use them up one bottle at a time, the keeping qualities of Rodinal type developers in legendary