deleting old snapshots

[Matthew Broadhead]

i am using 2.2.0 and i have looked through all the settings but i don't 
understand how to automatically delete old snapshots.

i followed this 
https://stackoverflow.com/questions/12315461/how-to-configure-maven-or-apache-archiva-that-it-keeps-only-n-builds-of-an-snaps 
but it didn't work