A second does not seem a very long time whereas 18 years might. On the exact anniversary of your 18th birthday, will you have lived for longer than a mole of seconds? A quick calculation will show that you have lived 6574 days, that is (18 x 365) + 4 days if we chuck in 4 leap years. This works out to be (6574 x 24 x 60 x 60) = 567993600 seconds. 5.68 x 108 is an impressive number of seconds but it is nowhere close...