Hello there,
from my experience (I'm selling in $500-700) range website, I would recommend waiting 96h and then file dispute, that's another 72h, so you have a week in total waiting actually.
During that time, on every day or every second day send them PM and send them message trough that thing "sales area conversation" anyway and send them email. All three, it sound's a bit spammy, but it's not, you want to make sure that they receive those messages as new users are not so familiar with flippa system.
I'm saying this from my experience, as I've noticed following. Person goes on flippa.com register and purchases my website (BIN) let's say for $500. He does not have that kind of money on his PayPal and he needs to upload funds.
Now, in that time he is not going to say "I'm waiting for money" or similar as that sounds stupid. He will just wait and pay you.
I'm saying this from experience and ton's of sold websites.
So, wait ~96h and then file dispute that gives you ~72h and you've waited enough, get your points back and start auction over.