Forums IMPORTANT: PLEASE READ PhotoReading, Memory Optimizer How many hours of sleep do we need?

I usually sleep 8 and more hours per night. Lately I've cut my sleeping hours to 6 - 7.15 hours and get sick quite often. I want to know how many hours do we actually need. If I persist and continue sleeping 6 hours a night. Will I eventually get used to it? Some sites on internet said that many people need more than 8 hours a night.. Maybe I'm one of those.