I've not rebooted any of my boxes in months, it's normal when you first turn them on for them to be a little slow, but in a minute or 2 that clears itself.
You should go into a little more detail about your setup, is this box in question the PVR or a remote box? How is it connected, hpna or coax? what's the model of the box in question?
Have you rebooted/reset the box? There's been several firmware upgrades, perhaps your box needs a nudge. (Press and hold the power button as well as the ok button in the middle of the circle, when the light flashes, let go, give it 2-3 minutes to reboot and see if that fixes it)