The individuals you have named are deceased.
You might have named someone as a beneficiary, executor, guardian, trustee or power of attorney who is now deceased. It is necessary to update the documents to insure that replacements are appointed.
New people should be named in your will (e.g. birth, adoption).
You might want to include a child, grandchild, niece or nephew who has been borm after your last will was signed. If you have named individuals specifically and not as a class, you will have to make sure after born individuals are included.
Divorce or separation or marriage
This might result in something as simple as a name change or as complex as trust planning to protect assets for your children and from a divorcing spouse. Most people do not want their ex-spouse to be a beneficiary, executor, trustee etc. They also do not want the ex-spouse to have control over assets that are left to their children and need a trust and third party trustee to protect the assets. This can be a top of the list reason for changing your documents.
New state laws.
You need to periodically check to see whether your state has enacted new laws that impact your estate planning documents. More importantly, if you move to a different state, don't assume that your will made in your previous state conforms to the requirements of your new state. Each state has its own legal requirements for making a will.
Change in guardians, personal representatives, or trustees.
As time passes, the people you appointed may no longer be appropriate for the various jobs. You must continuously review the people named and the jobs they mightneed to assume. Are they still the best choice? If not, change your documents to insure the best result.
Substantial increase or decrease in the value of your estate.
There might be federal estate tax or state inheritance tax issues that will depend on the esate value at the date of death. These tax considerations could result in significant cost or savings for your estate. You must be continuously aware of the tax thresholds and the planning needed to protect your assets.
The acquisition or disposition of a significant asset.
This might impact your overall estate plan or might necessitate specific mention of the asset in order to allow for the best transfer mechanism. This will only happen if the documents are updated as required.
IRA and 401K Beneficiaries
You should see an attorney about the best way to designate beneficaries. You should also have your wills and trusts drafted in a way to allow a trust for minors or for a spouse to be named as beneficiary and still have the retirement "stretched" for income tax purposes
If a beneficiary bcomes disabled, you must update your will to insert a Special Needs Trust (SNT). The SNT will allow the assets to be protected for the disabled beneficiary and will prevent them from being disqualified from government benefits.
Spouse has Entered a Nursing Home
You must update your wills to insure that some portion of your assets are protected from your spouse's nursing home spending if you die before him or her. This is frequently missed and cost the family tens or hundreds of thousands of dollars.