All puppies are small dogs – some, however, won’t be small for very long. You have to know how big your dog is going to be when it is fully grown before you can buy it a bed of its own, unless, that is, you don’t mind buying your beloved canine friend a new bed every six months or so for several years.The beauty of small dogs is that for the most part they are full-grown in under a year or so. You can count on certain breeds merely doubling in size from birth – starting out at about four to five.