If there was payment clearance time involved, I usually message the buyer informing them of exactly when it has cleared. And post the same or following day.

Sometimes PayPal automatically changes a payment to an echeque if a buyer is buying a lot of items and/or expensive items for secure reasons. The buyer is often unaware it changed and an echeque can take 3-6 days to clear.

You could also reiterate your handling time in the description as many don't see it in the postage section.