Thanks, I'd read that and, sorry to say, it is the source of my confusion. Is my "original date of travel" the date of my flight out or is it the original date of my flight back?
If it is the return date and I want to stay for a year, then I can't buy the ticket until just before the anniversary date - otherwise I will hit up against the year of the ticket's original date of issue. In other words if I buy the ticket in May, 2022 I would have to rebook the return no later than May, 2023 (rather than July when I want to travel).
Or, and maybe this is my ah-ha moment, are they saying I have to change the booking before the original travel date (the return date, not the first flight date), but that change can be for a more distant flight.
Maybe trying to explain myself I finally understood what they are talking about.
Have you checked if there is a price differential between booking the trip as a round trip versus booking each segment as a one-way trip. If there is not a material difference, you have options for the return segment..... a) book now for as close to your intended flight date, and then wait until you are in the reservation window for your desired July date .... and then either rebook when it first opens up, or monitor prices over time and rebook when there is no price differential to you original booking..... b) do not book the return segment now, and wait until the reservation window opens.