Another thing to check is if there is any specific time of day, and if there are any on-demand or batch campaigns running at that time.

In a multi-user instance this can easily happen.

Also, if there are mass CRM updates going on around these times, that can also cause a backlog and the sync to be delayed.

Not that this should affect what you are doing, but just a note to keep in the back of your mind!

See you in Vegas!

-Geoff