The only reason I can see is that you can always get ammo for a 30-06. The lovely 7x57 is not common but usually you can hunt some ammo down. The 318 .... It may be best to buy 2 or 3 cases and enough loading components now for the rest of your life. Maybe that's the solution, sell the 30-06 and buy ammo/components for the other two.

Great pair by the way.

If there is a more boring round then the 30-06 it must be the 308.