Any recent experience on these upgrade offers? How far in advance can these be confirmed?

My question is specifically related to the El Conquistador Tucson.

My issue is I have two rooms reserved. I have requested the upgrade to a 2-bedroom suite via eStandby for an extra $151 per night on one of the rooms, which I would gladly pay, as I would no longer need the second room. The problem is, if I don't get the upgrade until day of check-in, it will be too late to cancel the 2nd room (without penalty).

Anyone had any luck getting these upgrades when checking in on the app? Or do you have to physically go to the hotel check-in desk?

I am Diamond, in case that matters.