A few months ago I replaced my front tyres and the difference was astonishing. More confident acceleration, steering much sharper in the wet and dry, braking distance much reduced.
Last week I changed my back tyres. Certainly a little sharper in turning but not the same leap in driveability as I got when I changed the fronts.
If you want to mitigate against disasters you should line your houses with lead, fill an underground store with canned goods and put your freshest tyres on the back. Alternativly you will see the best real life return for your investment by putting the new tyres on the front and not letting the back go bald.
When my front tyres are down to 2mm I replace them. When the back goes down to 2mm I replace them. No faffing about. Simples