How far back into a drivers history do you think an insurance company should go when accepting a new policy holder?

If you were running an insurance company and had a 45 year old applicant how far back into his driving history would you go?

If a 45 year old was involved in an accident 15 years ago, would you ask him about the details or would you simply say what happened 15 years ago is no longer important?

I'm asking these questions because I went to pay my premium today and there was a guy there trying to get insurance, he said his last accident was 15 years ago. I left and didn't hear the rest.