How much time do we have until our products get dirty?
A product gets dirty in the same amount of time it takes to display it. So, a 4-hour product will get dirty 4 hours after it is ready to be delivered. For example, if you display a 2-hour pair of shoes at 4pm, they will be dirty at 8pm.
A product that was cleaned up by a visiting neighbor gets dirty depending on the game servers, but usually stays clean for about 1 week.