If you are talking about overnight, then you will lose funds on both the transfer in and the transfer out, which is also true of the longer periods, but I should think that in ten years that would be overcome by the increased value.
Bitcoins, I think are a good way to store money as long as you are storing them for long time, because in coming time the price of bitcoins will take a high jump and cross the 1000 USD mark very quickly.