If you're in an atmosphere, most of the time it doesn't really matter how far you fall, you'll hit going at about (rather, slightly above) terminal velocity. For planets without atmosphere, see trawum's post, above.
Perhaps add a delta-v map of the system and talk about the reasoning behind rockets having multiple stages (fuel tanks have a mass ratio of 9:1 wet/dry - lim(m->inf) ln[(M+m)/(M+m/9)] is only ln(9), or something like 2.2, which means that no matter how much fuel you keep adding to a single stage, you're only going to be able to achieve a delta-v of something like 2.2x the specific impulse of the engine.) Although you may wish to describe it a little more coherently than I just did.