I've done a couple of searches on the following questions and have not seen any specific answers:

1) I realise that paid $$ upgrades are not offered on all flights, but if a Y->C paid upgrade were to be offered on a given flight, is there a "typical" point in time the system starts to offer them? I.e., does someone have a better chance of being offered an OLCI paid upgrade if they check in 24 hours before the flight is scheduled to depart or if they check in closer to departure time? Does it matter if check-in is done more than 24 hours before the second segment of a two-segment flight (i.e., flight 1 departs in 23 hours, the connecting flight actually departs in 30)?

2) If one I have already checked in via OLCI can I check out and then "re-check in"? Would this increase the chances of being offered a paid upgrade? Alternatively, if paid upgrades are going to be offered and I go to the kiosk to print my BPs, would the system offer the chance to buy an upgrade at that point? Or would I have to ask a check-in agent/GA?

I'm already checked in for two segments from Asia to IAD via NRT and am happy with my Y+ seats, but if a paid upgrade were an option, I'd probably consider it. However, I don't want to unnecessarily jeopardize my seat assignments by playing around with OLCI.

I'd appreciate any advice/sharing of similar experiences.