I tried setting some events up to loop a timeline, and my first attempt to just replay on the timeline end condition doesn't seem to work as I expected. Looks like it is bug, i'll be looking into it.
It looks like you are doing everything ok.
At the moment the Set Keyframes option, will always attempt to create all missing keyframes at any given position, this includes the master keyframe and any property keyframes. If there are already keyframes at the position, they will be updated with what ever is the current value.
If you wan't to ignore some keyframes when playing a timeline, you can disable them. This is similar to deleting them, but if you use Set Keyframes again in the same position, no new keyframes will be added on top of the disabled ones.
You can select multiple keyframes at the same time by pressing Ctrl (Cmd in Mac) as you click on them. It is also possible to make a rectangular selection to select multiple keyframes at the same time by pressing Alt while you hold the pointer down and drag the mouse.
I hope that helps.