I'm posting this before reading all the replies, so I apologize if I'm a day late, a dollar short, or just not very helpful.

I did Nova Sure on a Wednesday last June. I did a Half Ironman the Sunday before, and a Sprint tri the Saturday after. There was no down time.

And I have not had a period since. No cramps, no monthly ANYTHING. The only regret is that I didn't do it years ago.