This is simply incorrect. I'm assuming you're talking about the Primordial Saronite requirement - you need 25 of it to advance the quest chain, and they can be purchased for 23 Emblems of Frost each. I'm guessing your "max 2 x per day" line comes from the limitation on 2 Emblems of Frost from the daily random heroic dungeon reward. It's true, you can only get 2 Emblems of Frost per day that way.
But if you're assembling Shadowmourne, you're doing more than running random heroics. You're also raiding, in Icecrown Citadel. And raiding in Icecrown Citadel nets you plenty of Emblems of Frost (as does completing the weekly random raid quest), not to mention the fact that Primordial Saronite is a drop inside ICC. Oh, and you can always purchase it from other players. If you're regularly raiding, consistently running your heroics, and not blowing all your Emblems on gear, it shouldn't take you more than a couple months to get all that Primordial Saronite, and much less if you're willing to buy it. And besides, Shadowmourne is intended for the hardcorest of the hardcore. It's not expected that your average WoW player will even be pursuing it.