[[ Not theory, not technical, but if you're interested in policy... ]]
It's a sensible idea to provide a renewal schedule for photographic ID, to account for changes in appearance and to "time out" tokens which might have weak physical security. So passports, for example, force renewal every five years for children and young adults and every ten years for old adults. The photographs are reasonably up-to-date (although five year old children can travel on photographs of them as a baby, which might not be good news in custody disputes) and passports only have to withstand a maximum of ten years of attempted forgeries. For example, recent EU passports have the passport number perforated through each page, presumably to defeat the swapping in of pages with visas, or swapping out of exclusion stamps. Older ones don't, but within ten years of the introduction of that security measure, all passports will have it. Attackers might choose to forge or modify an older passport, but they can't choose to manipulate a 1994 Blue British Passport with handwritten details and a photograph glued in, because even if they were able to modify the expiration date, the physical design itself has expired as well. So when photographic driving licenses were introduced, there was a lot of noise about the photocard portion having a ten year renewal schedule, the same as passports. This way, the photograph would always be relatively recent, and at least no worse than a passport photograph. However, it was a lot of work issuing photographic driving licenses, as it required photographs to be endorsed and validated and scanned. Once the passport office started scanning photographs and signatures and printing them in passports, rather than physically attaching a real photograph and sending them out for the bearer to sign, the solution was obvious: link driving licenses to passports, so that the same photograph was used for both. Provided you have a passport, you can apply for a driving license in the same name with the same photograph, modulo other proofs of shared identity. And you can do this irrespective of when the passport was issued. Can you see the problem? I've just received my first photographic driving license, applied for using the "linked to a passport" process. My passport was issued in 2003. So my new driving license, valid until January 2023 (when I will be 58), features a photograph taken in 2003 (which I was 38). I can drive, perfectly legally, in 2023 with a _twenty_ year old photograph on my driving license. So, why do we need to renew them every ten years? OK, the anti-forgery aspect of it is an issue. But most uses of driving licenses as driving licenses, rather than as ID cards, are checked online with the DVLC. Because you can't have driving license until you're sixteen, the ability to forge an older, weaker driving license isn't of much use for the main use case of posing as being old enough to buy alcohol, and I seriously doubt that even the Level 1 Security features in the license [1] are in reality checked by publicans. ian [1] UK Driving License Security Features