I re-validated my NPPL recently and got my club CFI to sign the license (well, the few scraps of A5 paper that I carry around).
There's no point not doing it, although I can see that it would be difficult to make a case against you, if you had flown the hours.
Surely there is enough money in the NPPL license fee for the license to be like a passport type document, something that we could be proud of showing people.