There are actually a few common things that can happen in your life that have an impact on your estate plan and they can be listed, according to the Huntsville Item in "When should you review your will?" The problem with making specific lists, is that people take them as exclusive, instead of as examples. People think only those things listed would require changing a will, when those things are just some of the common examples.
A last will should be reviewed and changed anytime there is a significant change in your life that would make you want to dispose of your estate differently. You do not need to think too hard about what counts as a significant change. It just needs to be something you find significant.
One way you can avoid having to think about when to review your last will is to just go ahead and review it every few years.
If your estate plan no longer accomplishes what you want, an estate planning attorney can advise you on revisions.
Reference: The Huntsville Item (May 7, 2018) "When should you review your will?"