What is the time frame of a DPC?

In the corridors of power galleries, a debate is going on about the time frame of a DPC. UPSC has reportedly informed one ministry that if a DPC is held, it is valid for 18 years. Administrative sources maintain that it is valid for one year. Some sources said that DPC minutes are valid for only six months. Experts said that it is totally unacceptable that after so many years still debate is going on an irrelevant subject, which clearly indicates, no one is interested in giving promotions to eligible officers. This uncertainty arrived when some ministries reportedly wrote to UPSC for holding DPC. UPSC is the nodal agency for organising DPCs for higher positions. Now the question is - who will clear the air?