There are always risks involved when signing a player to a big deal; those risks are amplified when said player is on the wrong side of 30.
In Mark Giordano's case, it was going to be tough: he'll be 33 years old when his new deal, worth an annual average value of $6.75 million, kicks in. That's not the problem. The problem is he'll be 38 years old when it finally expires.
Right now, it looks great: just under $7 million for a defenceman who should be a multi-Norris winner at this point? Awesome. But as the years go on, it has the potential to get really ugly.