Stale connection issues

When first got Sky at this address, the router stayed connected for 20+ days with no issues. Recently however, I have noticed that after being connected for 3 or 4 days the connection goes stale. We come down in the morning and, although the router is still connected, there is no throughput at all. At this time, the router has to be rebooted for normal service to resume.

Is there anything in particular I should be looking for as a cause? I have recently (last month) fitted a Samknows whitebox, but that is connected to a network socket in the rear, so shouldn't really be interfering with anything. I have contacted Samlknows customer service and they havde also said that there should be no effect.

Thanks for the input.