When you get a new puppy, you may not be planning to visit the veterinarian's office for several weeks, especially if the puppy is up to date on vaccinations. However, a vet visit is about more than shots. New puppy checkups should always be done within 72 hours of getting a puppy.
One of the biggest reasons to get a checkup fast is that some breeders give very limited guarantees. You may need to have your puppy seen as quickly as 24 hours after you bring it home to be sure there are no problems to take advantage of your breeder's guarantee. While the breeder may just be concerned that the puppy could be exposed to illnesses or injured during a longer guarantee period, a puppy should really come with a much longer guarantee than this. Still, if that is what you have to work with, take advantage of it in case there are problems you aren't aware of.
Another reason to get a checkup right away is that the vet can look at your paperwork to make sure your puppy really is up to date on shots. He or she may notice that your puppy has a gap in shot records or hasn't received an important vaccination. A phone call from the office staff to the breeder's vet should verify whether the records are complete and you'll be able to get your puppy off to a healthy start.