It should be noted that this duration is considerably longer than we naively expect. If two players with 500 dollars each toss a coin until one is ruined, the average duration of the game is 250,000 trials. If a gambler has only one dollar and his adversary has 1000, the average duration is 1000 trials.
Chapter XIV, Random Walk And Ruin Problems, p. 349. - An Introduction To Probability Theory And Its Applications (Third Edition)