8642HDC hard reboot - how often is reasonable?

I've had an 8642HDC for about 5 years now (no other equipment).  Every so often it gets stuck when trying to delete a recording and requires a hard reboot (unplug and plug back in).  Watching TV still works during those failures and the guide still works, but the DVR seems to get corrupted.  The box gets light use and is always less than 50% full in terms of recording capacity.

What is considered "reasonable" in terms of having to hard reset the box?  every week? month? day?...   I don't mind resetting it, but it does take quite a while to get back running again...