I don't think so, I do remember with SSRI's 6 to 9 months was an average for it to work after 9 months to a year, and all dosages have been brought up to the highest reccomended dose and not much response has occured or has stopped, that usually is when the doc will switch you to a different one. Your increased dose is most likely the dose needed to be therapeutic for you, and feeling better now, doesnt mean you should just stop them now or way before 6 -9 months, it's so important to go with the plan the doc who is treating you with the medication.
Stopping or shortening the time needed, can create further problems, always check with your doc, to play it safe.
Dosages aren't really what determines treatment length, but in some cases can. Some disorders are permenant and meds are a fact of life, but you can live "normal" while on treatment plan, so the life long deal of the med is fine vs not being on a treatment plan.
Some treatment may only be for a few months, allowing the brain to balance, which many meds can do for brain chemical imbalances.
Nothing is ever in stone, but that was pretty much what I heard from my pdoc, that many of the SSRI's poop out after awhile,and I learned that with my own experiences,before he switched me to Lamictal, when it came to the fact Antidepressants weren't helping anymore and that a mood stabilier was more beneficial.
What Lmo stated is very true.