The European 1-MW, 170-GHz continuous wave industrial prototype gyrotron for electron cyclotron resonance heating and current drive on international thermonuclear experimental reactor was during 2016 under test at the Karlsruhe Institute of Technology (KIT) test facility. In order to optimize the gyrotron operation, the tube was at first thoroughly tested in the short-pulse regime, with pulses that did not exceed 10 ms, for a wide range of operational parameters. Then, and after proper conditioning of the tube, the operation was extended to longer pulses with duration up to 180 s, which is the maximum pulselength possible at the KIT test facility. In this paper, we present in detail the achievements of the long-pulse experimental campaign.