Dependency can vary between substance users. Not everyone who takes drugs becomes dependent and the length of time for someone to develop a dependency can vary. For those who develop a compulsive dependence the cycle of addiction can be a harrowing seemingly never ending cycle of highs and lows physically, mentally and emotionally.
Each person is different and the time it takes to completely break free of the addiction cycle can vary from months to decades. The important thing is to try and keep trying until you succeed.