How old can tyres be before they need replacing?

When should I change tyres on my car? Is there a maximum age they can be?

Do tyres have to match?

My front driver's side tyre on my Toyota RAV4 has a slow puncture and I'm wondering how important is it to brand match, tread match etc. tyres when you replace a tyre? Should I move the two rear original...

We had the front tyres on our Sportage replaced and Kia says this has broken the four-wheel drive system?

We had the front tyres only replaced by a local tyre company on our Kia Sportage. Kia says the difference in tread between front and back has broken the four-wheel drive system and will cost £2k to repair....