Are you really interested in find out? Well that is a very good and reasonable question, well, an honest dealer should sell them as "demos" or "B stock" most of the times being honest mens to loose a considerable amount of money on them (talking for personal experience here, not sure about other manufacturers, dealers). That is why I'm really against those extensive tryout periods in which the amp sometimes even deteriorate due to missuse and improper care...
IMO a week is more than enough to make up your mind, in a few days, you will like or not the amp, and period. To buy an amp to compare it with 3 more, orderd the same way, and then return 3 of them, or the whole 4 is indeed really sad and a no no in my book, I'm completelly against of the abuse of the generosity of the return policies, any...