I believe they are now adding the points of all three throws. I think there is a maximum of 90 seconds if you do not lose the top before that time.
If all throws count, the three combos should be different or you will get less points because of repetition.
If the best two count, you can repeat one. Or, if you are already happy with your first two throws, you can attempt a very risky one for last.
If only the best throw counts, you could repeat the combo every time.
Hroch should confirm all these as I imagine he is in charge of the rules.