The TopSider pulls out oil via suction. Suction is broken when an air gap is introduced, as when you are nearing the bottom of the pool of oil. Remember when you are drinking your cola with a straw and you get to the bottom? Now try draining a cake pan with a straw, and don't move the straw. Can you get all the cola out? I DON'T THINK SO!!!!
Therefore, you can NEVER get out all of the oil using one of these devices, because you can never reach all the oil in the 12"x18" oil pan (which is like a cake pan's bottom).
Therefore, by draining the oil out, WHEN IT IS HOT OR VERY WARM, is the only way that you can be sure of getting all the old oil out.
That said, the small amount of oil left by the TopSider (and the residual dirt in that little bit of oil) is then diluted by the 6 quarts of new oil that you will fill, and therefore, it is not very important.
The benefits of a TopSider is that you do not have to crawl on your back, loosen the oil drain plug, get oil all over your hand, risk spilling some on your floor, and then having to put the drain plug back in again before you replenish the oil. Is it worth it? Only you can answer that question. Remember that it does take time to keep pumping all that oil into the TopSider. And remember that your oil will drain by gravity, while you do soething else. And remember that the TopSider was developed for marine applications, where it is "impossible" to lift the boat and drain out the oil. And remember that these kinds of "fixes" are for people who don't have lifts or patience to do it the "right" way.
Other than that, you pays your money and you takes your chances.......Andras