AFNI version stamps don't change very often -- every few months, typically. However, minor updates are recompiled frequently, typically once per week.

The current version stamp and compile date can be seen when you run the interactive AFNI program, in the text message displayed at the top of the window in which you type 'afni'; for example:

GPL AFNI: Analysis of Functional NeuroImages, by RW Cox (rwcox@nih.gov)
This is Version AFNI_2007_05_29_1644
[[Precompiled binary linux_gcc32: Aug 21 2007]]

This is from the edition I compiled last night. The longer ago your version was compiled, the more out of date it is. If your version doesn't show the compilation date, then it is several months out of date at least, since that's when I added the compilation date printout.