Buyers who pay via eCheque should receive two emails from PayPal - one at the time of payment, which (if they read it) lets them know the seller has been advised not to send until it clears. The second one is the notification that their payment has cleared, so if they pay any attention to their inbox at all, there's no reason to mark the stars for postage time down due to payment clearance time. 

Cuts the dispute time frame a bit in a way, though, if the 45 days is counted from the date of payment but there's a week or so where nothing can really happen.