Ramblings of an itinerant rocket scientist...

I disagree, of course. This is an interesting conflict between avoiding future obligations (if you always ask and are bothered, I incur an increasing obligation) and not losing control in the present (by asking for something personal). In practice, after a couple of lunches, we'd probably settle into alternating the invitations (to balance the control-issues temporally) or else I'd try to offset the favor owed to you with a different, cancelling favor (say, always picking up the check).