That depends on the strain that you are growing.
If you have an indica then 6-8 weeks,if its a sativa then 10-14 weeks depending on wether it is a pure sativa or a hybrid
I'm growing Mango and BB too, Mango is about 7 weeks for me BB takes about 9 weeks. With my BB it smells like fuel, when it mellows and smells more berry like it's almost time...I start my flushing then.