Pork in cry-o-vac will not age as long as beef will. Why? Dunno but it doesn't. I would say Sam's 21 days is a not only a sell by, but "use by" as well.
By the way, beef that has been wet aged over 30 days will have a "bloom" when first opened. A very robust "beefy" odor that should dissapate within an hour. Pork will do the same but keep in mind, there's "bloom" and then there's "stink" If your pork stinks, it's gone. Chances are, it will be slimey as well. If you're thinking, "well...it doesn't smell too bad"...be sure you're stocked up on plenty of Charmin