I'm still very new at roasting, but I've already found that the 1st/2nd crack AIR temp start and end times are very good indications of how far along the roast I am, along with judging by color as well as smoke aroma. As far as roast level recommended BEAN temps, I don't use them while roasting on a whirley pop. The thermometer I use only measures the air temp rather than the bean temp. So when using temp, I only base it on my previous roast temps rather than aiming for a desired bean temp for a specific roast profile. In any case, if you know what color and smell you are aiming for, then I guess it could work even if you can't hear the cracks. However, hearing the cracks is a good indication of how far along the roast you are.