In the post, you say the function is called StartEffect yet in the script it's called TimedEffect. I don't think either is very suitable, though. The function AddTimedEffect sounds good because it's style follows the related Blizzard's function, AddSpecialEffect (perhaps even better would be AddSpecialEffectTimed). The TimedEffect function should be similar to it's native counterpart, DestroyEffect, hence why I think the most suitable name is something like DestroyeffectTimed.
Also, you should include some short documentation on the use of the library in the library itself, not just the post, since users might get your library from maps that use it rather than from here.