Just about everything in LMS is schedulable. However, it sounds like you're asking about DFM polling. While you can adjust the DFM polling interval, you cannot set exception windows (i.e. non-work days).
However, what you could do is suspend these devices in DFM manually (e.g. on Friday), then resume management on them when you begin the following week. This can be done on a per-device basis under DFM > Device Management > Device Details.
Another thing you could do is simply suspend the notification subscription for your non-critical devices at the end of the week, then resume the subscription on the next week. This is done under DFM > Notification Services. Just pick the type of notification you have created (e.g. E-Mail Notification).
By suspending the notification subscription only, DFM will still be monitoring these devices, and producing events and alerts. However, you will not receive the emails/syslogs/traps for those devices when you do not want them.
