While a change in marital status, a change in financial status, the birth or death of a beneficiary or fiduciary named in your plan, or the purchase or sale of a business are four good reasons to review and update your estate plan, another good reason is because you've changed your primary residence from one state to another.
Once you've gotten settled in to your new home, you'll need to have your estate plan reviewed by an estate planning attorney in your new state to insure that it doesn't need any fine tuning to comply with the laws of your new state. For example, Florida law requires that the personal representatives named in your last will and testament be related to you by blood or marriage and if they're not, then they must be a Florida resident. Thus, if you live in Illinois and named your best friend from Chicago as your personal representative and then you move to Florida, you'll have to update your last will and testament to either name a relative or a friend in Florida as your new personal representative because your Chicago friend simply won't be allowed to serve.
Another common problem that I run into is when clients who had their advance medical directives and powers of attorney drawn up in their former state try to use them in their new state. While in theory these documents should be valid in the new state because they were valid in the old state, often times many doctors, hospitals, and financial institutions get nervous when the forms are different from what they're used to seeing. Also, sometimes the laws of the new state will require an advance medical directive or power of attorney to be signed in a different manner than the old state, such as in front of two witnesses and a Notary Public instead of just two witnesses. Thus, it's always a good idea to have a new advance medical directive and power of attorney drafted in your new state because this will tend to make your life easier.
Aside from this, because of the multitude of changes in the federal estate tax laws that began in 2001, many states have now enacted their own state estate tax laws. Thus, you'll need to meet with an estate planning attorney in your new state because while your estate may not be taxable for federal estate tax purposes, it may very well be for state estate tax purposes. As such, if you do find that your estate is taxable at the state level, then you'll need to explore your options for minimizing the estate tax bill as well as your options for paying the tax.
Suffice it to say that if you change the state of your primary residency, then you should sit down with an estate planning attorney in your new state to insure that your estate plan will continue to work as you intended.