'Kallis used to do it' is hardly a convincing argument given he's about the only bloke who's ever managed it! Also Kallis mostly didn't bat 3, or bowl as much as Stokes, and usually had the luxury of batting behind an obdurate top 3. The average opening stand for England since Strauss retired is a little over 12 overs.
You could say that, but then you'd be ignoring the fact that Stokes is usually the 4th seamer and so can if necessary have a good rest before he bowls. He's a good batsman, it'll do for now, but can't see it going for much longer.