SOS is available at lord 35 as long as you spend the available skill points into the right positions. You can reset the lord skills at any time for 1000 gems (800 from merchant)
After you have SOS you have a decision. Spend points in development again (to harvest) or stack out your war stats. I keep harvest for quite a long time but due to azurite do not build often enough to warrant having build speed points.
Note that I show you from my lord level 43. I will need to change spec again for lord level 44 and slaughter as this again requires a direct route.