Most people don't realize that pigs never really quit growing but slow down after reaching about 4 yrs of age. They will grow approximately 50# of their adult weight in the first year; then about 25% for the second and 25% for the third yrs but then will really slow down.
When breeders tell you that they will never be over 35 - 40 lbs, they are selling for the money and not telling the truth. Although breeders have done a great job of breeding them down in size, if you look at our history pages at http://www.farec.org you will find that the first ones that came over and into the United States weighed in excess of 225# when they died. Because of that genetic come into play and size can never be guaranteed. Also the smaller they are as adults, they develop more health issues.
So please do your homework first. Then consider adopting versus buying from a breeder. Rescues will be truthful as they are not in it to make big bucks.