Silver, I believe you have interpreted the rule correctly. There is a pre-defined time for fall assuming that you don't come into contact with anything solid, and the spell tends to go away as soon as you land.
On the other hand, I try to keep things open. What if a wizard came up with some elaborate plan to fall from a cliff, land on a floor, step over to a pit, then drop to the bottom. If this could all be accomplished within the spell's time duration, I'd probably allow it. I like to encourage clever ideas from players and would prefer that the rules not get too much in the way of a nice plan.