The top notes of a scent usually go off first. If that's the case, it should become what you expected a short while after application. Otherwise, I'd think you know if it was completely off. You really wouldn't get anything nice from it.
If you're initial blast is pleasant and spicy, chances are your juice is fine.
I have not sampled Patou PH but this has been my experience from many years with other scents.
Lastly,don't forget that the aftershave might not be exactly the same as the EdT.