Muffin is chipped but Cracker is not. I lost Cracker for 3 days in south Texas. The rancher called from the field when she jumped into his truck. She has a snug collar with phone numbers on the name tag.
I know that they make some of that fiction I read in books. I read in one that the chips had a life span of about 3 years.
When chips first became available many years ago, they had a bad habit of migrating to other places. I remember one dog whose chip was properly placed atop the shoulder area and within a year the nomadic chip had moved back to a rear leg. The design of the newer chips make them stay put where they belong, and they last indefinitely....certainly much longer than a dog's lifespan.
The early chips also tended to tend to have one of two frequencies, depending on the maker, and the detecting devices could only read the frequency of just one type. Nowadays, the detectors will usually read both frequencies.
Every pet or hunting dog should be chipped--tattoos are largely obsolete now--and a brass nameplate on the collar is a good idea too. Every pound, SPCA, veterinarian, etc will have a chip reader. And the nameplate may keep your trigger-happy neighbor from shooting your dog, should it get loose.