I give most buyers 7 days until I send a reminder. Many of my long term buyers are given extra time and each case is different.
Many times I get a special request to hold off on paying me because they might not have the funds or some other situation. Recently, someone asked me to wait over 3 weeks until they pay me. I said no problem. Three weeks go by and buyer said that they no longer wanted the card. It's stuff like that which annoys me.