I need to do something similar. However, in my case, having just a start and end event would be insufficient, as I need to exactly know what portion of the way through I am, like with a keyed interpolated property, even when adjusted for timescale, pausing, or anything else.
The context is that entities can jump or slide from its starting position to the targeted enemy as part of melee attack animations, and the game needs to know how far through the jump/slide it is so it can position the visual appropriately. (And I can't use some kind of constraints to do the whole movement through Spine, as there are things involved in the runtime outside of Spine). I can imagine other uses for such a durationed event as well, such as other visual effects that are handled in the runtime outside Spine.