Thank you, yes I'm talking about the tier benefit upgrades.

I suppose I could book economy and request the upgrade, then if J is filling up, consider changing plans and booking business directly or altering the dates? Or would a change forfeit the upgrade, even though it hasn't been confirmed?

Concierge waives change and refund admin fees, I see. Do you still have to book a changeable and/or refundable ticket to take advantage, or does that tier render all tickets changeable/refundable?