There is always a contingent of posters who seem to insist "Space available as determined at the time of check in " in the T&Cs is meaningless, that all upgrades are given at the absolute discretion of the property, and one must grovel and be grateful for any upgrade generously given by the property to a Diamond member.

This is absolutely not the case, because if it were, no property would ever issue an upgrade and hang onto inventory in the hopes of selling it to another customer.

The terms may leave some discretion, but it's certainly not absolute. Significant availability shown in Hilton's inventory, within the definition of what falls within the T&C definition of an "upgrade", for the same period as one's stay is absolutely grounds to question management on why an upgrade is not being provided.

In fact, Hilton's public statements regarding "3 day advance upgrade notifications" for Diamond members made it quite clear that was to be the norm, not the exception.