pc's, laptops, phones etc. if left on 24/7 and/or in standby will get slower and slower and freeze/hang thus needing a reboot. The same goes for set top boxes (stb).
Switching it off into standby doesn't help, it needs to be physically restarted, i.e into standby, wait for disk activity to stop if applicable then power off at socket or unplug, wait 10 - 30 seconds and restart for a proper reboot.
This will happen from time to time, more often when using red button and catch-up and more often when the stb has a hard drive. Nothing at all to worry about it's just one of those things and no need to change how you use the box.
I've not noticed needing to reboot our hb1000s, but we do get power cuts from time to time which act as a reboot. If you notice the box getting sluggish it'd make sense to reboot it at a convenient time to restore normal performance.