When will US withdraw its troops from Korea peninsular?

Comments on Robert Edwin Kelly “Comparing North Korea to East Germany”, 9/04/2011, http://www.eastasiaforum.org/2011/04/09/comparing-north-korea-to-east-germany/

Should the two Koreas be unified and given China's the relationships with the Koreas, why will there be any need for the US to have its troops stayed in Korea at all?

Let's acknowledge it, China has not stayed its troops in North Korea since the truce in the peninsular and the US has had its troops there.

The former USSR collapsed and the cold war has ended now for over 20 years. The US still has its troops in the peninsular

So how long will US troops stay in there and what its purpose will be and who will they be against?

Whether the Koreas are unified or not, or when they will do so, there is always the question: when will the US withdraw its troops from the peninsular to both symbolically and really actually contribute to a more stable and peaceful Northeast Asia and East Asia?

It is ridiculous for the US to use its military bases in East Asia to conduct spy missions over other countries. Would the US accept others to do the same spy missions using planes or ships around it?

If this is what the US means for China to follow the rules, is that a just requirement?

You have the military power to project forces to anywhere in the world.

You have military bases bordering others.

You have nuclear arsenals to destroy the world many times over and you have the means to deliver those weapons in very short time to anywhere.

You have much superior technologies in nearly every combat areas.

You have invaded so many countries, for one reason or another, including Iraq that was pre-emptively conducted and is still going on.

You constantly spy on others.

You also bombed China's embassy.

You harassed China's ship in international waters.

So still, you want others to follow this rule forever?