As you have time, I would seriously consider finding some way of getting enough points to pay for a hotel, through credit cards or other promotions.
Hotels in central Amsterdam tend to be rather expensive.
It's not so bad at the airport, but then you may need a shuttle bus and train to get into the city, which eats up your short amount of time there.
easyhotel.com would probably work, and laterooms.com also have some smaller hotels.
Personally, after travelling that distance, I would want something better.