1. Your beneficiaries have died. What happens if your will leaves your estate to your two siblings, but both siblings die before you? If your beneficiaries predecease you, your will is still technically valid, but it will have no effect on who will inherit from your estate. Instead, your estate will be distributed according to the law in your state, just as if you had died with no will at all. 
2. You have potential new beneficiaries. A will that was written before you got married or had children will be of little assistance in distributing your estate. States have provisions that protect spouses and children that come after a will is written. In most states, spouses are entitled to a certain percentage of an estate. In addition, many states have laws that protect children born after a will was written, allowing them to inherit from the estate. It's possible that under the laws of your state, a spouse and children not named in your will may not receive as much as you would have wanted them to. In both of these circumstances, state law is dictating where your estate is going, not you.  
3. Your executor is dead or unable to serve. The executor (also called a personal representative) is the person named in your will who oversees the distribution of your property. If the person you named as executor is unable to serve, the court will have to appoint someone else. Beneficiaries may have a say in who is chosen, but it may not be someone you would have wanted in the position.
4. You no longer own property named in the will. Suppose your will attempts to divide up your estate equally by giving cash to your daughter and property of equal value to your son. If the property is sold before you die, your son will receive nothing. In this case, your will is no longer ensuring your estate is divided equally.
5. The law changes. If your estate plan was designed specifically to avoid estate taxes and the estate tax law changes, your will may no longer serve its purpose.

Contact us to ensure your will is still up to date.