I have been looking in to this for a possible First Class trip to Australia and New Zealand from Europe flying with Qatar and Cathay Pacific for the main long haul flights.
The distance travelled would be very close to 25000 miles . If I add BA flights to position for the main flights I would go over into the 25001 to 35000 band.

My question is if I go into the next band could I use the remaining mileage allowance to add another trip, 6 to 9 months after the trip to Australia?
This would be booked before we travelled to Oz keeping all flights within the allowable time frame for all flights to be completed.