Reaching your accumulation target to me is not an enough reason to sell your bitcoin. In as much as you may not hold your bitcoin time eternity but it's not wise to sell just because you've reached your target and you now are still in active service. Withdrawing at retirement or in an event of extreme emergency situation may be a wiser reason to withdraw your bitcoin.
If you have reached your bitcoin target and you are still very active financially and young in age, you can increase your bitcoin target and start accumulating towards your new target so that you can reach an over accumulation phase in your bitcoin investment. It's a wide decision because no amount of bitcoin can be enough for us if we have the capacity and resources to continue accumulating after we have achieved our bitcoin target. That gives you more room to increase our wealth in bitcoin.