Calling the correct weight for a dog is an art. The easiest way to 'find the eye' or 'learn the art' is to keep dogs in really good shape all year. Well fed, lean and fit, healthy and free of parasites, great housing, clean chain spots, etc..etc.. Even the best can't look at a dog 10lbs over and do a two week keep and call that perfect weight. Their best guess will be either lucky or wrong, usually wrong. And the opposite is true as well, wormy, underfed, 'skinny' dogs are a hard call as well.
What makes so many people think they have the eye is that the dogs can overcome the owner's inaccuracy with heart and talent, and in some cases mouth. Lots of times the dogs win in spite of their human counterpart. And one of the great human tendencies is to take credit where it is not deserved.
Lots think they can slop feed once a day, have no interaction with the dog, leave him in a filthy/unhealthy state then walk him for two weeks, upgrade his food, work for 6-8 weeks and end up with a world class athlete. Simply not true.
If someone ever says, "He really came on the last week or so of the keep", usually means he was fed like shit before hand and when he finally acclimated to the upgrade in 'fuel' and the benefit of exercise, he "STARTED" to shine. Further meaning, if the dog had started out at par, he would have SHINED earlier and SHINED BRIGHTER as the keep progresses/ended. And even then the dog has adjusted to the weight that was chosen for him not so much operating at the optimal weight. Take that same dog and allow him to live year round above par, then start and he will be SHINING from the jump and will get BRIGHTER and BRIGHTER as the keep progresses.
Calling the correct weight is a "year-round decision" not just so and so has a 41M and I think ol' Spot can go at 41, let's pull him down 7 pounds this week and call the weight. Ol' Spot better be a good one because he is basically on his own. EWO