Whilst I agree that responses do slow with age, so does the driver's speed, which helps compensate a little. From my own experiences as a driver in his 50's I also keep a healthy distance between myself and the car in front... even at 30mph. Only minor changes to driving in later years but it's the difference that insurance companies recognise and reward. I pay a few hundred pounds whilst 20+ drivers are paying thousands.

Dr C just beat me to it ^

RAC figures

One in five young drivers (17 to 24-year-olds) will have an accident within six months of passing their test and 1,552 young drivers were killed or seriously injured on Britain’s roads in 2011 – more than four deaths per day.