I found this:
Puppy Bladder Development | eHow.com
CONTROL:
Most puppies under six months cannot control their bladder for more than a few hours at a time. According to University of California's Davis College of Veterinary Medicine the frequency of elimination breaks should align with your puppy's age. The age/elimination guidelines are: six to 14 weeks/ eight to 10 times daily, 14 to 20 weeks/six to eight times daily, 20 to 30 weeks/four to six times daily, and 30 weeks and older/three to four times daily.