Without starting a new thread and the title is quite general here is my Q:

Upgrades with Miles at Check In-- how does it work-- How soon before departure? If there is a seat in (F in my case) the class avail (no an award seat) do they give it out then- or do you have to wait till the gate to be confirmed?

I wont bother turning up early if I cant get the seat on check in and use the F lounge-- will sleep an hour or so more at home instead!

the Flight I am going out on this week has 3 F seats avail at the moment- and never had any Z availability for past month for this flight.