Ofcom have released the amateur radio licence statistics for September 2013 showing a further rise in numbers

The grand total of licences at the start of September was 81888 an increase of 87 over the August figure.

“The new “lifetime” licence will remain valid for as long as the licence details remain correct or until such time as the licence is either revoked by Ofcom or surrendered by the licensee. There is no end date on the “lifetime” amateur radio licence but Ofcom will revoke the licence unless the licence is either amended or validated at least once every 5 years.”

— Ofcom

The first of these new licences were issued in 2006 but the licence statistics appear to show that none yet been revoked due to the holder failing to amended or validate it. Because of the impact of the Olympics, Ofcom did make the initial licences run for six years instead of five. This extension should have resulted in those licences that were not validated dropping out of the statistics after December 2012.

Since 2006 possibly as many as 3,500 UK radio amateurs have died and they would have been expected to drop out of the statistics, but month after month the numbers that Ofcom report show a steady rise.

There is no way of telling how many amateurs have simply given up the hobby in the past 7 years or how many amateurs there really are. The rumour mill may suggest that fewer than 25,000 amateurs have renewed their licence but the statistics do not tell us.

On March 14, 2013 a response to a Freedom of Information Request stated that "Ofcom have not carried out another extension." [of the licence], but it seems they haven't revoked any license either.

Ofcom UK Amateur Radio Licence Statistics - http://licensing.ofcom.org.uk/radiocommunication-licences/amateur-radio/guidance-for-licensees/monthly-stats/

How to validate your licence - http://www.essexham.co.uk/news/remember-to-validate-your-licence.html