Licence validity
A JAA-PPL has an expiry date of 5 years from the date of the skills test.
A NPPL is issued for life
A pre-JAA UK PPL is also a lifetime licence (unless you go back a lot of decades, when I believe they were given a finite life)
EASA PPLs will be lifetime licences again when they get round to issuing them in July. So, if you have a JAA-PPL, you should only need to renew it once after April, when it will become an EASA PPL.