PayPal Payments Standard Expiration

Question

I am using PayPal Payments Standard to upload contents from a custom shopping cart. i.e. The upload happens with a page redirect which posts the hidden vars to PayPal where the customer completes the transaction. When the transaction finishes, PayPal uses the "IPN" process to notify my the payment has been made.

In this case a reservation is made at the same time. The same as selling a limited stock item. As it wouldn't be good to have multiple PayPal transactions out there contending for the same slot, the reservation is made before the customer gets redirected to PayPal.

Once the Customer is at PayPal they might realize they don't have any money and close the window leading to an unpaid reservation that needs timed out and dropped.

Is there a guaranteed expiration time for the PayPal checkout page after which the reservation can be discarded without a risk of receiving a surprise payment for a deleted transaction? I realize IPN has it's own non-deterministic timing stuff, but without knowing there even is an expiration period, someone might sit on the website for a day and then pay.

Answer 1

Possibly too late to help you, but for the record: I asked PayPal tech support this question, as I couldn't find it in the docs either. They wrote:

Each transaction is associated with a token that expires after 3 hours if the buyer didn't complete the checkout. This isn't usually modifiable but can be extended by contacting a Business service representative ( we don't recommend to extend it for security reasons however. the token can't be less than 3H in any case)

So it's a MINIMUM of three hours.