They are offering 750points extra for any stay booked within the next three months.
You can book stays until December 2014, though you will have to reserve them within the next three months to qualify for the bonus.
To register you click here: Accor Offer
As I have mentioned before Accor are very generous with their points and offer. Currently they are offering 5x more Avios as I have mentioned in another article here. You can combine both offers to receive more points. 🙂
I know for many people it is hard to book stays well in advance, a way around this is to book a room that is refundable. If you can’t make it, then you don’t lost any money. 🙂