An estate plan is not like a pint of milk. There is no expiration date. However, while it can have a long life (all the way until you die), you might want to replace it with a fresh one every so often.
Why do this if it does not expire? Because your situation will change, and when it does, you need to reflect it in your plan to ensure the changes are covered.
Here are some reasons you might need to review and update your plan:
Things turned sour
Relationships, whether a marriage or a business partnership, do not always work out. When they end, you need to split the assets, which could significantly affect what you have left to pass on.
Divorce will also affect who you want to leave things to, meaning you probably need to change not only your will but any beneficiary designations where you had named your spouse.
To stop people skimming the cream off the top
If you have considerable wealth, the tax office will look at skimming some off the top when you die and pass on things. Passing assets on before you die or placing them in trusts can help you reduce your taxable estate.
Another reason to reduce your estate is Medicaid. They will be keen to charge you for any healthcare you need in later life. Reducing your assets early reduces the chance that they can.
When you find a new cash cow
Maybe you start a new business that goes exceptionally well. Forgetting to add this to your estate plan could mean your heirs miss out.
If there have been changes in your life, seek legal help to update your estate plan.