Long-haul flights which are refundable long in advance

Reasonably priced flights are usually non-refundable. Some airlines also offer refundable flights, where for a fee they can be cancelled and refunded, often right up to the day of the flight, but they're understandably much more expensive. Do any airlines offer anything in between? Flights that are cancellable, but only quite some time in advance, and at a lower premium.

The background here is that I'm arranging a holiday at the end of the year, and we want to book flights soon, partly to avoid being caught out by price rises, partly so we can begin booking other parts of the holiday, and partly because flights are needed before we can apply for one of the required visas. However one of the group is worried the holiday dates might clash with a conference he has to attend but the date of the conference won't be announced until the late spring or early summer. Our flight itinerary is quite complicated and will cost around £1000 in total, which is more than he is willing to lose if he has to drop out of my holiday. Equally, if he has to cancel it will be several months before departure, and he's loathe to pay a £800 premium (which is what it looks to be) for fully-refundable flights as he's happy he won't need to cancel at short notice. I'm wondering whether there might be some other style ticket that allows cancellation up to a couple of months before at a more reasonable price.

Two long-haul legs of the itinerary dominate the flight costs. We're currently thinking of using Emirates, but there are literally scores of airlines offering similarly priced alternatives via different hubs, so information on any major airline with long-haul routes between Western Europe and East or South-East Asia is potentially valuable.