48 hours/2 days, but you won't be able to book two offers with 2 days between online. You can book one offer but you'll need to call TR and tell them to book the second offer after two days. Try and have the two days you pay for fall during the week so the price of the room will be less expensive on the two days you have to pay will be less expensive.
Alternatively, if you can bag the second offer for a while and just book your offer with 5 comped days and use a second CET offer at the end of your trip.
The third option is to bag the second offer altogether and see if a host will book 7 days for you and use just one offer. That's what I did for my April trip. A reservationist, however, will not be able to book 7 comped days for you. A host will need to do so.