If the object could be acellerated to the speed of light, there would be no way to slow it down, because if an infinite amount of energy was used to speed it up, there would be none left to slow it. Its motion throught that dimension would have become irreversable. The reason that no object has ever been reversed in its motion through time is that there is not enough energy in the universe to reverse time's flow. Everything is hurtling through time at roughly 186,282 miles per second. The fact that nothing has ever been observed moving from the present to either the future or the past further serves to prove that Einstin was right in computing light sped as the ultimate speed limit.
Nothing can move faster than light in either the three spatial dimensions or time.
Although this theory is untestable at least with our present technology, we may some day in the future be able to determine it. Only time will tell. The reason time's influence is less at high velocities is because all three spatial dimensions are oriented differently than the flow of time. Any speed in any direction opposes that flow.