During the 2003-2006 thriving market, I was 100% in equities. I am a very "nervous nellie" and that was very tough for me to do, but I needed a much larger nestegg and essentially gambled and won. Once my nestegg had grown quite a bit I moved to 80:20 and then 60:40 (equities:fixed) which was MUCH more comfy for me in accumulation phase.
I figured that I wanted a more conservative AA than that in ER, so two years beforehand I started moving towards my target AA of 45:55 (equities:fixed). My timeframes were really speeded up, though, by necessity. I think most people start to make their move much earlier than that. Anyway, at two years out I went from 60:40 to 50:50 and pretty quickly to 45:55. I wanted to try 45:55 during this final year so that I could get a sense of how my nestegg would work for me after ER, to get a better feel for it.
As has been pointed out, the market helped me out in getting to 45:55. I am now 13 months out.
I would say that a good reason to make your move would be if your present AA is uncomfortable for you at present, in accumulation phase, during market ups and downs.
You have quite a bit of time until ER. Still, at about 5-10 years out I think most people would want to be much closer to their retirement AA than earlier. You don't want to risk all you have worked for unless you have enough time to gain it back.