All I have to say is it seems like an awful waste of fuel. The next damn plane better be carrying a payload. (preferably nuclear)
They don't fly over North Korea. The U-2S, RC-7s, RC-12s, RC-135s etc stay in South Korean airspace. The North Koreans have the missile capability to down a U-2 the same way as the Chinese and the Russians have done in the past. The recce flights stay in international airspace - far too vulnerable to go risking crews in this manner when the job can be done from stand-off sensors onboard.