We have a cheap Freeview box on a TV in the bedroom. In the past it has very occasionally needed the programme guide to be updated - maybe once every few months. It's a process that takes six or seven minutes, during which you can't watch TV - you just see an on-screen message and small revolving thingy.
This also happens on the rare occasions that the Freeview box is switched off at the mains.
But over the past week this process has happened almost every time I've switched it on from standby - I reckon five nights out of seven. We haven't had power cuts, and I know the unit has been switched on (on standby) the whole time.