Long-running job

Upon login to an AFS machine, a user is automatically granted a "token" by the Kerberos authentication system. This token allows the user access to directories in AFS where that user is explicitly allowed access, such as the user's login directory tree. Without a token, a user is in the category "system:anyuser" (anonymous), and has access only to those directories where system:anyuser is explicitly given access rights.
Tokens are on a per-machine basis: i.e., a user's tokens on machine-A and machine-B are not related
To check token status: /usr/afsws/bin/tokens
Tokens man page: man tokens (/usr/afsws/man/man1/tokens.1 on afs1.njit.edu - afs36.njit.edu)
The default token lifetime is 25 hours; to request a longer token lifetime, up to 500 hours, send mail to sys@oak.njit.edu

If your executing program is reading or writing files, you will need to make sure that your Kerberos token does not expire before your job ends. The best way to do this is to log in to to the machine on which your job is running often enough so that the expiration time of your token is later than the expected finish time of your job.
Your processes on a given machine will inherit whatever the current expiration time of your token is. Upon logout, your processes will retain your token expiration time as of immediately before logout.