Well, they say Pluto has an orbital period of 248 years, but it was only discovered 1930. Do we really have to sit around for 248 years "to be sure" that Pluto's observed pattern really
is an orbit?
Granted, the 2400 year period for 2M1207b was picked out of a hat--there's no telling at this point how eccentric its orbit is.
But 2M1207b and 2M1207 were recently both shown to be a "common proper motion pair". If they're not in orbit around each other, what else would they be doing hanging around together?
But my main point is just that we are getting useful data about planets that are not ultra-close to their parent star.