What are the effects of a will during the lifetime of the will-maker?
Wills don't take effect until the death of the testator (i.e., the person who wrote the will). The process that gives a will legal effect is called probate. The probate of a will cannot happen untel the testator's death. During the testator's lifetime, the will is ambulatory and revocable.
Wills are ambulatory
A will doesn't have legal effect while the testator is still alive. Let's say Henry makes a will that leaves $1000 to his brother, Bernard. Henry is still alive. For as long as Henry is alive, Bernard doesn't have any right to the $1000.
Wills are revocable
A will can be changed or revoked at any time during the testator's lifetime, as long as the testator has testamentary capacity (see Making a Will in Virginia. So, if Henry and Bernard have a falling out, Henry can change his will. Henry could revoke the will and create an entirely new will, or he could amend his will to eliminate the gift to Bernard. (And Bernard would not have any recourse since wills are ambulatory).
For how long is a will valid?
Wills are valid until they're properly revoked. Let's say Henry, at age 30, makes a will. Henry takes his will home and puts it on a shelf in his office. A few years later, in an effort to free up shelf space, Henry moves the will to the basement. He never even thinks about that old will--or any other will--again. It sits in the basement until Henry's death at age 75. The will is still valid. In order to prevent the will from becoming legally effective upon his death, Henry would have needed to revoke the will.
How can a will be revoked?
The process of revoking a will is a like the process of making a will in that there are rules. In order for a will to actually lose its potential legal effect, the will has to be properly revoked. There are a few ways to properly revoke a will.
This is where the testator cuts, tears, burns, obliterates, cancels, or destroys the will or his signature with the intent to revoke the will. The destruction doesn't count unless it's done with the intent to revoke the will. Accidental destruction of a will won't count as revocation, because there's no intent to revoke. So, if Henry shreds his will without realizing the document he's shredding is his will, he probably hasn't properly revoked his will.
Henry can revoke his will by executing a new will that says it revokes all prior wills. The key to making this revocation effective is that the subsequent document must be executed with wills formalities.
How can the contents of a will be changed?
Let's say Henry comes into a lot of money and wants to leave Bernard $10,000 instead of $1000. Can he just write in the extra zero on his will? No. In order to effectively amend his will, Henry would have to reexecute his will or add a codicil.
Make a New Will
Henry could create a new will. In order for this new will to replace rather than supplement the old one, Henry would need to revoke his old will.
Add a Codicil
A codicil is an amendment to a will. Henry could use a properly executed codicil to change the amount Bernard gets. A codicil is a separate document that amends an existing will. It has to be executed the same way as a will.
Sometimes, state law will alter a will. For example, if Henry omits a child, under certain circumstances, state law will treat the omission as unintentional and give the child a share of Henry's estate. (Note: it is possible to intentionally disinherit a child or spouse.)
It's important to take care when trying to change or revoke a will. There are rules for revoking and making changes, just like there are rules for making a will.