When are Shore Experiences/Excursions charged for during a world cruise?
Shore experiences booked on board during a world cruise are charged at the end of the sector in which they are booked.
If you wish to pay for shore experiences within a particular sector, then they must be booked within that sector – there is, however, a risk that your chosen tour may be sold out.
You may find the following question useful: What are the payments dates for on board accounts on Round World Cruise sectors?