It differs between each one. Some stand up at around 5 weeks, and some take a couple months.
Generally between 4 and 6 months
The procedure is usually done with Doberman Pinschers, Boxers, Boston Terriers, or Great Danes. Generally, ear cropping is performed when dogs are between 9 and 12 weeks old. After this, the chances of success drop, as Fido’s ears may already be drooping.
All dogs will, do, and need to chew. However, if you train your dog at an early age not to chew, they will not.
For a small breed like a boston it would be about 10 months. You can switch it to adult food.
varies, but should be erect by 6 months
Most dogs are cropped between eight and twelve weeks of age. Any older than this and the ears would likely not stand properly.
Ear mutilation is usually done around 9 to 11 weeks of age. Any later and the ears may not want to stand. You are trying to find that time when the puppy is old enough to handle the butchery and anesthesia well, but young enough that the cartilage is not set in their ears yet.
When a chihuahua is young, the cartilage in its ears hasn't become strong yet. Depending on the day and the dogs behavior, the ears may or may not stand up. When the dog has reached a certain age (sometimes 6 months or more), its ears should permanentely stand up. Also if it has adopted a trait from one of its relatives, the ears might never stand up. So sometimes it's just genetics.
They will eventually stand up on their own, although the exact age is different with every puppy. I have seen a few that had one ear stand up completely and the other ear stand up only part way. If you see this starting to happen you can massage the ear in an upright postition and it will help strengthen the ear and help it stand.
All dogs are different. Some will grow whiskers when they are a few months old. Others will start when they are two years old! All dogs are different!
6 to 9 months
A healthy Boston terrier can live anywhere between 15 to 20 years of age.