I do exactly as you do re eCheques and bank deposits in terms of marking the item as paid or posting the item. It is the safest way, although I have obviously been lucky (so far) and none of the many eCheques which I have received over the years have bounced, although I have had numerous "non-payers" who made no attempt to pay.

On a separate but related subject, if a buyer makes a 'typo' when paying on the internet by direct / electronic bank deposit, it can take several days for the funds to 'bounce back' into the buyer's bank account (assuming that the incorrect BSB / account number is not by coincidence a 'real one' belonging to somebody else!), and the buyer is not notified by their bank. When buyers have gone through check out and marked that they have paid by bank deposit, if the payment does not appear in my online banking statement after a few days, I email the buyer and ask them to please check their bank statement to look for a "bounced back" payment. The few times this has happened, the seller has apologised and re-paid with the correct BSB & account number. When buying and paying by bank deposit to save the seller PayPal fees, I usually copy & paste the BSB and account number to avoid this happening to me...