Being fair , those of us who have had their FAC for many years should and could be given a lot more than 5 years terms on RF especially . The argument for brain fade with age etc is easy counters via the simple fact the medical records are shown to the GP who would be part of the loop ! I think if we run the stats there is more logic to examining decline in driving in my personal experiences and cars are the vector of far more deaths and serious injury far and awayIt's long been understood as an issue. See clauses 4.17 onwards
https://assets-hmicfrs.justiceinspectorates.gov.uk/uploads/firearms-licensing-targeting-the-risk.pdf
Forces have tried to mitigate the peaks and troughs in workload in different ways including what S Wales police is doing by offering some people a 3-year cert. One of the arguments for moving to 10 year certs was a BASC proposed model for balancing out the peaks and troughs, which would mean phasing in longer cert life, ie. not everyone would be getting 10 year certs straight away, it would be phased in.