I think there is an optimim time to take an AOW course. If you take it too early, you do not really have the skills or experience to fully benefit from an AOW course or fully appreceiate the finer points of the skills involved. On the other hand if you wait too long, all you are getting out of it is a patch as if you have been diving with a more experienced mentor type buddy and/or have worked to constantly improve your skills, you will have most likely acquired all the skills taught in AOW through experience.
In my case I got certified in college as they offerred PADI Open Water for one credit and PADI Advanced Open Water for a second credit. I completed both courses, but since AOW did not really mean anything at the time, I opted not the pay the extra $185 for the AOW cert. Since they were semester courses college courses they involved a lot more dives and class lecture than PADI required, but I still think AOW would have been more worth while with 25-30 dives in between.
About 1000 dives later, I discovered that I needed an AOW C-card to get me in the door for more advanced training and to offcially certify me for some of the things I was already doing. Consequently I got an SSI AOW card by picking up 5 specialties and learned absolutely nothing since I had been doing nitrox dives, night dives, deep dives, dry suit dives, wreck dives, underwater navigation, boat dives, spearfishing and underwater photography for years and was a repair technician. So they had no specialties that offerred anything new. Obviously somewhere in between 10 and 1000 dives was the optimum time to take an AOW course.
