I agree with not buying into the shoot up ammo before it gets old. However, I also believe you should shot plenty of the SD rounds you plan to carry to make sure they function correctly in your gun.
Some guns are finicky when it comes to HPs, though usually handling just about any FMJ. Some will eat any HP you feed it, while others prefer certain ones, and then some are just plain unreliable with any HP. For this reason alone, you need to run many rounds of the SD ammo you plan on carrying just to make sure it's reliable in your gun.