The amount of time it takes for hair to dreadlock depends on the dreadlocking method used, maintenance techniques, as well as the Texture of your hair. Some methods cause the hair to lock quicker than others and coarser, tightly coiled hair locks quicker than straighter/wavier hair.  Thus, there is absolutely no way to state a definite time frame at which your hair should be locked.

To make matters worse, even though you may have a particular hair type, the speed at which it Dreadlocks depends on where it's located. For example, the hair at the nape of your neck or at your crown will generally be looser (less coarse) than other areas. Therefore where your sides may be locked, the nape or crown may have a few more months to go.

In general, you should expect the majority of your hair to be locked within a year, but don't plan on reaching full maturity until you're about 14-18 months into the game.

My Friend Lock'd Sooner
Good for your friend.  Their hair isn't your hair.  Do not fall into the trap into believing that the filthier your hair is, the quicker it will lock.  This is crap...literally.  As a fore mentioned, a number of factors can extend the amount of time it takes for your locks to mature.

For example, comb-coils and palm-rolls are the most difficult methods to care for during the early locking stages.  They frequently unravel, require to shampoo less often (every 3-4 weeks) and are not generally well suited for straight to loosely coiled hair.  Despite the disadvantages, these two styles tend to mature into locks faster than others...especially when the individual has a coarser hair texture.  So depending on your method and hair texture, you could feasibly lock within 6-8 months.  HOWEVER, if you're starting dreadlocks, prepare for your hair to lock no sooner than 12 months.  By setting this expectation, you won't allow yourself to become stres
sed.

One more thing, if you're free-forming, your hair will tend to reach maturity faster than any other dreadlocks method.  Most of the time when we speak of dreadlocks, we're referring to Salon dreadlocks but much of our advice applies to anyone with lock'd hair styles, no matter the method.

I'm Still Not Lock'd
There are some hair types that even after reaching the 18 month mark still haven't locked or, you may be 90% locked and  still have a few rogue teenage dreadlocks to contend with. 

To the left is a picture of naaniMODEL daezhavoo.  You can follow her dreadlocks journey via naani.com or by visiting daezhavoo.com.  In this photo, daez's dreadlocks are approximately 14 months old.  Notice, she's not fully lock'd!  Sometimes it takes that long people and rushing demonstrates a lack of understand and respect for your locks.

Avoid so-called dreadlocks accelerator solutions like sea-salts, lemon or filthy tactics like refraining from washing your hair.  The first two will damage and dry out your hair, your scalp and your locks.  The damage can be irreparable if these methods are used repeatedly. 

Second, where your locks may not "stink" if you don't shampoo them for months at a time, that's probably because they're not wet.  A dry, dirty dog doesn't smell as funky as a wet, dirty dog.  Those odors, that filth is being twisted into your locks for months on end.  And don't kid yourself, your hair is dirty.  Sweat, dust in the air, mites in your bedding, dandruff, product Build-up, it's all there.   Look at it this way, you may the cleanest person in the world but if you never dust, your furniture is eventually going to need a coat of polish.  The same goes for your locks.  The longer you go, the more you will never rid your locks of that ingrained odor. 

So-called solutions and quick fixes to growing dreadlocks can insure you one thing, damaged hair.  And here's the kicker, if you've never locked your hair before, who's to say that these solutions sped anything up?  How would you know if they're locking faster?  Harder, dryer does not equal dreadlocks.  You should aim to keep your hair as healthy as possible throughout your lock journey.  Healthy hair grows longer, stronger and faster.  Not to mention it looks better.