The auto-aklog Kerberos extension will automatically renew your AFS tokens when your Kerberos tickets are acquired or renewed. I recommend using this plugin along with the Kerberos.app ticket manager to avoid having to worry about keeping tickets or tokens up to date.
Currently, auto-aklog will test to see if you currently have un-expired tokens. If you do, it will only re-acquire tokens from the principal whose tokens you currently hold. If you have no tokens, it will get tokens for your default credential cache.
To install the auto-aklog Kerberos extension:
Run::
xcodebuild install DSTROOT=/
then edit /Library/Preferences/edu.mit.Kerberos. Under the section labelled "[libdefaults]", add::
login_logout_notification = "auto-aklog"
If you find any bugs in auto-aklog, please report them at http://github.com/ebroder/auto-aklog/issues