You might have already reached Million Miler Lifetime Platinum with AA, but if not it might be worth considering if it is worthwhile to continue to credit to AA until you do, especially if you could reach it in a reasonable time frame. That way you could lock in Sapphire status. The flip side of that is of course if your travel patterns are heavy then BA Lifetime Gold may be achievable in the distant future, and anything you credit to AA pushes that further away.