I somewhat agree with this and somewhat don't. Labs can and usually are a royal pain in the ass for the first 12-18 months of life. Of course, this depends on the individual. Some dogs are perfectly well behaved from a very young age. Mentally, others might never mature and be "puppy like" right up into old age. It is a real mixed bag with this breed. At one end you have extremely active demanding Labs that are always on the go (field types often fall into this category) and at the other very mellow easy going Labs that take life as it comes. Breeding plays a huge part in this.
Labs are incredibly high-maintenance dogs