In my experience, the suite certificates are something to keep in your wallet and ask to use them every time. And start asking well before expiration, because you will get turned down many times on average before entering the hallowed suite.

Diamonds get Regency Club or Business Plan as the "next level up". I didn't think that the policy was "best available". If so, I will start walking up to the counter, asking if Suite number XXX is empty so that I can rent it for a night and when they say it is, yell "Aha! I shall take it for free as a Diamond!"

Somehow I don't think that would work. The Baltimore staff would probably take me out back and shoot me in the head, Baltimore-gangland style.