Pain in my butt (but at least he' polite)

Ben, my son, is a handful. I think that my mother described it best when she said he is like 4 two year olds all rolled into one incredibly energetic, incorrigible, messy, trouble-some kid. He gets into everything and he never stops except to occasionally sleep leaving me completely drained of all energy (truthfully sometimes I think that he's an energy sucking alien who uses my energy to power himself). My husband and I have been struggling futility to try and instill some discipline, good behavior and manners into him; however, as of now, we've only succeeded in one out of the three. Ben currently listens like a rock, causing us to ask him several times at day if his ears are simply painted on. There are things that he has been told not to do for over a year and a half (he's 2 and a half) that he still keeps doing, knowing that he will be punished but generally not caring. But it's his newest thing that has my husband and I struggling not to laugh most of the time. He's always had great manners, saying please and thank you when he wants something, sometimes even reminding us to say them including you're welcome which doesn't seem to make it into most conversations and we've been really happy with him so far, proud that he's this polite. However, now when we tell him to do something now, like "Time to go to bed", we get the simple response of "No thanks, Mom." This isn't screamed or yelled or accompanied by tears, all of which I'm used to by now, but rather said in a calm quiet voice that seems to defy argument. And he will keep at it, just calmly repeating his "No thanks" (actually it comes out no finks because he can't pronounce the "th") until someone usually picks him up and brings him to bed. On one hand, I'm thrilled that at times, there aren't as many tears or temper tantrums, but when faced with his calm response, I will admit sometimes I get a little flustered. But well, at least he's polite.