Under normal conditions, when the brakes are not very hot or very wet and frozen, when should a driver use the parking brake?

49 CFR 383.111(b)(7)(iv) – Parking brake; AAMVA CDL Manual, Section 5, subsection 5.4.8 (p. 5-9)

Treating the parking brake as an every-time habit, not just a precaution for long stops, is what prevents rollaway incidents during routine parking. The CDL exam tests this as a baseline habit, and the two narrow exceptions (very hot, or very wet and freezing) are the only times you should skip it in favor of wheel chocks.