I respectfully disagree with this. And FWIW, I have been "maintaining" since September--have actually dropped a few more pounds.
I think mentally maintaining is so much different than losing. It is so easy to get complacent and so easy for bad habits to sneak back in when you are not "on." But I have also been battling this for my entire adult life. And if you are a girl you get to add in hormones, etc to the mix. Maybe it's different if you didn't spend so much of your life in the heavy category.
I agree that it is probably easier to maintain than lose, however, for some people (myself included) it's definitely not as simple as 30 minutes of exercise a day and trying not to eat too much. I'm pretty sure that I read that women in their 40s and 50s need an hour of exercise a day just to maintain--don't quote me on that one.
Anyhow, I think it's just a little more complex than just do a little cardio and eat less.