A lie never lives to be old.

Falsehoods require maintenance, and the maintenance grows faster than the lie does. Each one has to be remembered exactly, kept consistent with everything said since, and protected from anyone who might compare notes. Time works against it, because the number of people who could contradict it only increases and your memory of the details only fades. Most are not exposed dramatically; they simply become too expensive to keep.

If you are holding one, consider that the cost of ending it now is almost certainly lower than it will be later. And where you are tempted by a small convenient untruth, price in the years of upkeep before you decide.