I prefer two hour temper cycles, a lot is going on inside the steel, and it takes time to happen. The tempering is where the steel becomes a usable knife blade, so give it enough time to work.
All blades should get two tempers. Any retained austenite will be converted to martensite in the first temper, and then that new martensite will be tempered in the second. The second temper also assures complete evenness of tempering in the blade.
Stacy