We have had several 1 star reviews from customers based in Australia and the US because they have received the feedback request before they received their order.
The 5-day delay we have set is perfect for our UK customers, which make up the vast majority or orders. I don't want to make this any longer, as customers will be less likely to respond after more time.
Setting the feedback request delay by region would help keep the functionality simple. E.g. being able to set it for Europe, North America, Australia, Middle East, Far East, etc.