All not staking coins and increasing your weight will do is put you towards the front of the line for staking rewards. All coins should get their % reward regardless of how network weight. There is obviously an advantage to getting your reward coins earlier as when it's all done you are in a position to sell earlier. However there is also an advantage to staking now, as a) you increase your holding, and b) you reduce overall coin supply.

I can see an advantage in stopping staking 24 hours before the last PoW block, so you can get right in there and grab your reward coins early on the first (and subsequent days)