You hit on both points I thought about reading the initial idea. I doubt I would want to do it for any reply but for helpful/correct within 24 hours I think it makes great sense. As far super users using it to their advantage, I would look to see how quickly they are answering questions to see if they are getting to them quickly or are they doing "sweep up" work after questions have been open for a while.
There are quite a few variables at play so the analyst in me would say that before I would make the jump on implementing a tweak like this I need to run several different usage scenarios against the current state to see what the impact to point totals would be based on user behaviors. Are the same folks still on top? Do new point leaders emerge?
After figuring that out, that's when I would make the call.