OXFORD – Modern medicine is redefining old age and may soon allow people to live regularly beyond the current upper limit of 120 years, experts said on Wednesday. It used to be thought there was some inbuilt limit on lifespan, but a group of scientists meeting at Oxford University for a conference on life extension and enhancement consigned that idea to the dustbin. Paul Hodge, director of the Harvard Generations Policy Program, said governments around the world — struggling with pension crises, graying workforces and rising healthcare costs — had to face up to the challenge now. “Life expectancy is going to grow significantly, and current policies are going to be proven totally inadequate,” he predicted.