Thanks for the info so far, even though it's not what I want to hear!
For context, selecting/changeing dates isn't the problem ... the reason for the questions is that I'd rather book once bookings are open, but it's a long gap between outbound and inbound (3 months) - so ...
Would prefer to grab fares before buckets are empty, upgrades before they vanish, and nice seats before they're taken, of course, not to mention trying to co-ordinate with getting bookings on other airlines for connections (including points bookings which vanish soon after 365 days out).
Sadly, EK don't seem to offer sensible one-way pricing, unlike some airlines, otherwise I'd just grab two one-ways.
(Pity there isn't such a thing as being able to book a return flight with a confirmed departure date under 365 days ahead, and, say, a set date for the return, even though it's over a year away ... that way they'd still have my money, for even longer, and I wouldn't have all the worry!

)
BTW: The fares would be J (with just enough points in the "family pool" to upgrade one way from standard flex, if my calculations are correct, and if you can do that from the family pool ... but's upgrades are less important than airfares and seats!)