The five day test was me back in July. I was in the dealership back in May ordering some parts shortly after they they registered their demo S3 and the salesman came over to tell me that I'd really love the car and that I should take it out for a test. I told him I wouldn't be interested in buying it but that I wouldn't mind a quick spin some time he was free. I pass the dealership most evenings on the way home, so I told him to give me a shout some day when he wasn't too busy and I'd pop in.
One evening in mid July I got an email from him to say that rather than giving me a quick spin they thought I would enjoy an overnight. I replied that that would be ok and that I'd pick it up the following Thursday - he replied and told me I could keep it until monday. They figured that the longer I had it the more willing I would be to buy it. I handed it back after 5 days and he called me the next day looking for 25 grand along with my 18 month old car to change! I politely declined, told him I would have put the cost to change at nearer to 10 grand and asked him to give me a shout in three months when it hadn't sold. Like I said, I pass the dealership every day and it is still in the window at full price. My brother was telling me yesterday that he was in with the dealer looking at their R8 during the week and he told him that they'd be reducing it to 45 grand (from 62) fairly soon. They won't even get that because it is a MY07 car (but registered in May 08) and it is now the old shape. If he'd come in at that kind of price at the start I might have tried to haggle him down a bit. Not interested in it now though - much rather my own car.
I guess it depends on the dealer, your relationship with them and how much they want to sell you the car. You might find a salesman is more likely to give you an extended test towards the end of a month or quarter when he has sales targets to meet - in the current economic climate this might be easier than before.