Does a freeview box have to be permanently plugged into the mains?

hope this is the right category.
Some people have told me if I get a freeview box I will have to keep it permanently plugged in, either in use or in standby. I never do this with my TV so why would a freeview box need this?
they say it would need to be retuned each time I plugged it back in.
I'm guessing digital TVs don't need constant retuning each day so why would a freeview box?
or are these people wrong?
I'm not getting one if Ihave to leave it on standby when I'm not watching TV.