Hoya kasterbergii finally bloomed with three flowers this month, but it looks like there are more buds following. So I may see more blooms before the winter is out. Here are the exact conditions under which it finally bloomed:
Temperature: Night time 55-60 degrees Fahrenheit (12-15 degrees Celsius) Day time High 77°F (25°C). Lighting: Combination T-5 Fluorescent and LED lamps. Humidity: Day time RH 55% and Night time at 85%.