I would be deliriously happy if eBay allowed a transaction to be cancelled due to non-payment after 4 days (or other time-frame specified by the seller) rather than keep the 4-day second chance tacked on to a UPI dispute. 

I would be even happier if they applied buyer requirements to all accounts held by that person rather than letting repeat offenders get a clean slate for doing nothing other than having more than one email address (eBay reps have been known to advise buyers to create a new ID for the express purpose of circumventing a seller's blocks, which is just outrageous). 

NPBs aren't my greatest concern, but they happen often enough for me to wish the above, as well as harbour some minor resentment for paying what they cost me in order for them to window shop and tie up my stock.