The raising temperature idea comes from treating the fresh water version of ich, which while it has a similar life cycle is a totally different protozoan. Raising the temperature will speed up the life cycle slightly, but unless you are keeping your tank rather cold, not enough to make a real difference, besides the SW ich likes the warmer temperature unlike the FW version. Since raising the temperature doesn't have any real benefit to the fish, and is actually optimal for the ich, I personally don't see a point in raising the temperature.