Some really good points there Irene.
The art of good effective marketing is to highlight the positives and down play the negatives. I'm with Irene here, when I see a listing with some disclaimer (usually written in big red letters) I AM NOT RESPONSIBLE FOR ITEMS LOST IN THE POST, AND WILL NOT REFUND, or some other type of thing, the very first thing that says to me as a buyer is ..... this sellers has problems with items going missing in the post, and if mine happens to be one of them, then the seller is not going to be of any assistance at all!
That all adds up to a BIG no sale from me!
It's a good idea when writing your listing copy to write from the perspective of a buyer, not as a seller. Ask yourself what sort of information you would like to know if you were buying the product, then ask yourself what would put you off buying the product.
As Irene has said, you need to set your conditions out clearly, but make them professional, and don't dress them up as something that amounts to nothing more than a threat.
Another thing to keep in mind when contemplating your conditions is to be sure that your conditions are within eBay's own policy guidelines. For example, it takes 96 hours after the auction has closed till you are able to file a non-payment dispute against a rogue buyer. Therefore it is a little crazy to have payment terms where full payment is required within 48 hours of an auctions close.
Work to eBay's own guidelines, if you want to ensure cash flow, then set your payment terms at 96 hours, it's not like you can file action against them to recover fees before then anyway, and it creates a more flexible payment term for buyers.
Make sue you are able to enforce any terms and conditions that you do set, for example: Stating that you will not be responsible for items going missing in the post is a little crazy if you are taking PayPal payments. You have no choice if you are not sending the items with tracking to begin with.
All the customer has to do of course of file a claim with PayPal, they will ask the seller for proof of postage, and if a seller can't provide them with a tracking number as proof, they will find in the buyers favour and award them their money back anyway. All you are doing is putting buyers off to start with by listing that sort of rubbish warning!