Like others on this site, I am considering using encfs + sshfs for secure offsite backups. I am wondering how robust encfs is to brute force attacks? Do some users use the --stdinpass command with a file to make it harder to crack?
Depending on the reliability of your password (how secure it is), it should be effectively unbreakable. It uses high grade encryption from everything I could find.
Note that storing the password on the system you are running encfs on will make it useless. That is, if you store the password in a file on the system itself, it won't take long for an attacker to find it and use it.
If you must store it somewhere, try a USB flash drive, or type it.