We paid as requested during regular visits (total $4K) for first boy's braces and got around $2,200 back from the health fund. That is the total of ortho work they will cover for his lifetime.
Second boy we did the same but chose to pay in a lump sum in one financial year so we could at least claim some rebate as we were over the health threshold that year.
It meant we had to have the funds to pay, but we got everything back we were entitled to (and a bit more through tax - I think it is dental and medical to reach the threshold?) and didn't have to pay in dribs and drabs spread out over a couple of financial years and keep sending off claims. I think this was prior to Hicaps and I had to post a claim off, which was a PITA.