Are you certain that your end users are utilizing strong passwords on your Linux servers? Let a tool called John the Ripper (JTR) show you who is and who isn't. Learn how this is done in a helpful tutorial.
The security of your Linux servers is only as strong as the passwords used by your end users. If your users have weak passwords, it's only a matter of time before any given ne'er do well breaks into your system to wreak havoc on your network or steal precious data.
You don't want that.
So what do you do? You can certainly set password policies, but even then, you might have a user that predates the policy or maybe you've set a policy that borders on weak.
To make sure your users aren't working with weak passwords, you can employ a tool called John the Ripper (JTR) to make sure those passwords aren't easily crackable.