Dynamic smart lists for age groups

Is there a way to pull together a smart list for defined age groups and automatically updates with the appropriate leads?

For example, the age groups could be:

1. 24 years and under
2. 25 - 54 years old
3. 55-79 years old
4. 80 years and older

I can create a smart list using Date of Birth to identify these leads today (e.g. #1 would be "Date of Birth" after [11-Mar-1992]). But in a few months time, the leads age would have changed but not my leads list.

Any ideas?