In addition to the backup site server maintenance task, be sure to also backup these directories on every server that has them. It will make your restore, should you ever need to perform one, much smoother.
|SCCMContentLib||Usually largest drive on primary site server|
|SMSPKG||Largest drive on distribution points|
|SMSSIG$||Largest drive on distribution points|
|SMSPKG<drive letter>$||Largest drive on distribution points|
|Application/Package Source Directory||Wherever you store your application/package source files. This includes Applications, Packages, OS deployment WIMs, and driver packages.|
Look for a script soon from WME to do all of this for you on a scheduled basis.