Vista - Why schedule Sync if files are automatically kept in Sync?

I am using offline files to always keep my network files with me on my
laptop. This also takes care of backups as my files fall under the office
routine for backing up files.

I have two questions:
1) According to information in Vista "help", it is stated that files are
kept updated automatically. Is it still necessary to schedule a Sync? An
experience is that files in use generates errors if I manually start a Sync
in the Sync Center.

2) I have a bout 7GB of data on my network drive that I keep available
offline. Upon a manual Sync in Sync Center, it takes about one hour for it to
finish. Is this simply because there is so much data for Windows to go though
during Sync? With ref to question 1, if it always take an hour, and files in
use generates error messages, I'm inclined to stick to manually syncing every
once in a while when I am off to a meeting or similar....

Does anyone have some hints with respect to the above?

Many thanks in advance