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.
_________________Marv / FinarvynDCC Minister of Propaganda
; Deputized 6/8/11
DCC RPG playtester 2011, C&C
since 2003, ADRP
Since 1993, OD&D
player since 1975
"The worthy GM never purposely kills players' PCs, He presents opportunities for the rash and unthinking players to do that all on their own."
-- Gary Gygax
"Don't ask me what you need to hit. Just roll the die and I will let you know!"
-- Dave Arneson