THC half-life can vary from 0.8 days to 10 days. There are many factors that go into it such as body fat %, activity level, diet, smoking history, etc. Without access to a lab and multiple test there is no way to know what the half-life of THC is in your body. Some people are clean in a few days, others may take 60+ days.

I have seen studies that go both ways when it comes to whether long time smokers metabolize THC more quickly or slowly. Looks like you found the same thing. Best thing to do, get a home test online or from a drug store.