Mrsmac - not sure about what your FN has told you, but from my perspective, it has definitely not been easier after having had a child. We've been at it since my DD was one and a half, and are still at it more than a year and a half later. She took 6 weeks to conceive, and I guess we were lucky then, but it's certainly run out now.
As far as I'm concerned, certainly not easier.
ETA: this is a particular sore point for me at the moment. People in my circle ask when we are having another, or assume that we don't want another. I have told some people about our IVF treatment, and most have been understanding, and I've even found out some of them have had treatment too. However I've also had some insensitive and offensive comments about it, so sorry if my post comes over strongly. I know I'm lucky to have DD. Rant over