Rant - Buyer paying on the last day

Ok guys, am I the only one, who gets frustrated with the 7 days window for buyer to pay for the items? Recently a guy bought from me a few singles (on 1st Jan) and since I have scheduled leave starting tomorrow, I have messaged the guy asking to pay before 8th. He didn't reply at all, so I was planning on cancelling his order today, but get genuinely paid in last minute.

Asked for cancellation since I honestly can't send the cards in the next 7 days, but he rejected my cancellation. Feel like stacked between rock and a hard place here, guess he will get his refund after 7 days and I will get negative mark on my profile, but seriously - can't we limit the time window for sending/paying for merchandise to 3 days max? It gives people a reasonable amount of time to transfer money between accounts etc.

Just to add - as a seller, I am always trying to send cards within day or two since I know that people are usually time sensitive when it comes to online shopping (I am one of these people as well😀)