Hello! I know this is super late, but I thought I'd chime in just in case. I've been using NC for about three years after running across it at my local pharmacy and I love it. It works great with my schedule. I did read some worrying claims about it when getting started, but my country's medical authority investigated its claims and confirmed that they are accurate and that this does work.

I am always careful not to be tempted to "cheat" and record temps when I woke up a bit too early to be within the right window. I be sure to mark temps as invalid if I haven't slept enough etc. I always play it safe: I'd rather disregard a temperature when I'm not 100% sure that I took it correctly. Nevertheless, it's learned my schedule and I get a nice amount of green days each month. The rest of the time we use a condom.

Personally I was considering tubal ligation for years beforehand, but when I saw that this was an option and tried it that went away. I feel like I have the best of both worlds now: safe condomless sex with my long term partner without going through surgery.