Ok, let’s do some math. According to Lauren Faust, Twi is about 15 at the beginning of the show, meaning she’s 25 at the end. The Mane 6 is all around the same age, so let’s assume this is the case for Pinkie. Pinkie didn’t start throwing parties until she was about 5, so being generous and saying this is Pinkie just before the time skip that’s 20 years of parties.
20 times 365.25 is 7,305 days of parties. 1 million divided by 7,305 is just under 137 parties a day. Honestly, that seems pretty achievable for Pinkie.