If you write a will when you are in your 20s, chances are that it will no longer be accurate decades later. Fortunately, wills are documents to which you can make changes whenever you need to.
Nevertheless, it is necessary to make it clear which version of your will is most up to date to prevent disagreements and contests later on. Money Crashers describes different ways to update your will.
Revoke the will and write a new one
If you intend to make extensive changes to your will, it may be easier to write a new one altogether. You should give copies of your new will to your executor and retrieve any copies of the previous will and destroy them. The new will needs to include a statement explicitly saying that the old one is no longer valid.
Add a codicil
If you are only making a few minor changes to your will, you may opt to add a codicil. This is an attachment to the original will describing the additions and changes you are making to it. A codicil needs to be very specific about the changes it makes to a will, and it also needs proper signing, dating and witnessing.
In the days before computers, it was more common for people to add codicils to their wills. It took a lot of time and effort to completely rewrite a will to make a few simple changes. Computers have made document editing easier, and you may find it more convenient to create a new will than to add codicils. However, the way you make changes to your will is up to you.