Under what road condition should an auxiliary engine retarder or engine brake be switched OFF or dialed to minimum power on a heavy articulated truck?

1. When descending a steep dry mountain highway in summer
2. On slippery, wet, snowy, or icy roads, because aggressive retarder torque applied solely to the drive axle can break tire traction and cause an instantaneous jackknife (efecto tijera)
3. When driving in heavy desert heat
4. When carrying maximum payload on a straight dry freeway