In general a Will is valid until your death, but there are a few exceptions. If you were married at the time you made a Will and then later got a divorce, in most states either your entire Will was revoked or the portions of your Will that gave property to your former spouse were revoked by the divorce. The remaining portions of your Will might also be affected if the property listed in your Will went to your spouse in the divorce settlement or decree. If you intentionally destroyed the original of your Will or wrote a new Will that revoked it, that also would invalidate your Will.
A Will that has been revoked by someone who is legally competent cannot be revived; you have to make a new Will. So, for example, if you have a Will, then change your mind and write a new Will saying that you revoke the original Will, if you change your mind again and destroy the second Will, that would not make the first Will valid again. You have to remake the original Will.
Though your Will remains valid if you havent divorced, it makes sense to update it regularly if your situation changes, such as by losing contact with your named Personal Representation (or Executor/Executrix) or by changes in the property you hold. For example, if you sell your house and buy a retirement condo, you need to update that information in your Will. Of if you wanted to leave an equal inheritance to 2 children, but the property you left to one has increased in value, while the other has lost value, you might want to make adjustments to your Will.