I gained my (lifetime) CAA PPL in 1996. At that time I was of the age that a CAA medical was only required every few years. As I progressed into my 50s the medicals became a more frequent requirement and at £150 a throw it paid me to take out a (lifetime) NPPL against a 5 year sign-off by my local GP at a cost of £12 (plus self assessment prior to any flight as normal, of course). Provided the limitations were accepted, the cost of the NPPL was covered in the first 12 months. Plus, provided that I have currency, I can revalidate my full PPL at any time by simple compliance with that licence's medical requirement. Kind of best of both worlds.