I have 8-10 scents I wear all the time . Conservative estimate of approx 4 sprays per day , maybe 2 sprays for 2 different scents. That gives approx .5ml used per day or around 185ml per year. 6 of these scents are used in yearly rotation. Maybe 2 are used less so. By my calculation I need no more than 35ml of each scent throughout the year. 100ml is the max size I will go for in any scent now. I figure approx 3 years of use is just fine and then time to restock.