Wireless keyboard "vanishes"

[Seymour]

Thankfully, I have never had any issues with wireless keyboard connectivity. It works without any "tweaking". After a few hours of inactivity, it still brings my XBMC back to life (from the dimmed state). However, if I leave it for a day or so, and come back to the TV, XBMC is still showing but the connection to the keyboard is lost and I have to power-off to get re-started. The dongle in the hub is still powered as the led still flashes with key-presses. I t seems that there is a time threshold where the keyboard connectivity is lost and cannot be recovered.

Could someone explain this please and advise of a workaround that will keep the keyboard active.

Thanks