Fair enough. But, doing so with the intention of “holding” a suite and then still getting it even without the upgrade instrument is trickery.

A better approach in my opinion would be to not upgrade initially, wait, and then apply the suite upgrade IF availability indicated using one.

Furthermore, I have absolutely no idea how one would expect to know what the hotel’s actual availability is before arrival. Online availability of suites at full price is not a reliable indicator of an hotel’s actual, physical occupancy levels.

They’re just free upgrade certificates. If you want a confirmed upgrade, use one. If you’re willing to take a gamble, do not use one. Using the upgrades as part of a strategem to game the upgrade system is not proper.