Once upon a time, it was recommended that domestic electrical installations were inspected every 5 years - only very few actually did.
A cunning plan was put into place to increase this period up to a maximum of 10 years as the current BS7671 suggests that any work should have a minor works certificate issued indicating that basic tests (earthing, insulation etc.) were satisfactory and therefore problems should be nipped in the bud.
This cunning plan works as well as most other poorly thought out plans and even inspections are now part of the 'I can do that cheaper/better' department.
I've lost count of the number of Inspection reports that bear little resemblance to real life, even when carried out just a month or so previously
Still, it's better than nothing!.