I did not ask a general question because I wanted to know. I asked because it was impertive to my parnassah. I happen to know some Chashuv people (Not MO Chashuv either) who know exactly what I do and how I make my income. I do not wish to say who I asked because it might give away part of my identity.
It is possible on Amazon and ebay for vacation settings., However on eBay even with vacation settings a sale could still take place especially if you write you will be returning from vacation tommorrow (Meaning Sunday) . On Amazon there is an option to send your inventory to Amazon where they warehouse the item, Sell it for you and ship it for you. There is no way to shut that off. Once Amazon has the item in their possession they will ship as needed. You get alot more sales that way so its nessasary to do so in order to make sales.
Perhaps the Rabbi from the Business Halachic institute was talking about a general website as opposed to eBay and Amazon where it works differently and its not really possible to shut down for 25 hours.