There's not a setting for that per se, but you could schedule a Refresh Inventory task to run daily (or as often as you want) against the "Inventory not collected..." group. Just create a task targetting that group and save it. Then locate that task in the Tasks folder, right-click it and choose "Schedule...". This will pop open a Windows Task Scheduler window that you can specify to run at intervals you want.

Would work. Just be careful with running a refresh inventory on such a broad group of machines. If you have a machine that needs a client update (the monitor icon with the exclamation point), and a refresh is run on that machine without it being connected to ghost, it will revert the machine's name to the mac address in the console...which sometimes makes it hard to figure out what that machine is.

Just an annoyance that I've found with refresh tasks that I thought I'd share :) 

One thing to address that would be to check the option to use Wake-on-LAN on the network tab, so that it wakes machines to run the task.