I'd be interested to know how nesting is broke. I know some things are all chicken, and egg as far as who made who goes.
Also Aurel's workaround with is overlapping sounds interesting, but I think there should be some other way to do that.
You have to keep in mind that that is one of the "gotcha's" of frame rate independance.
Is overlapping is bound to be more expensive, I will say that much. Plus trigger once is a little iffy, a better solution may be an instance variable.