I started having problems after a few months, with random reboots and lock ups.
I tried so many different things to pin down the cause, and had so many theories - power fluctuations, bad spots on the disk, overheating, internet dropouts, buggy code.
Like you, I always had content to watch and couldn't find an easy way of backing it up to watch or restore later, so I never found time to reformat the disk, to rule that out.
In the end I was lucky enough to get a second Skippa and, after swapping the disks over, finally realized that the problem was there. I ended up biting the bullet and exporting, deleting or watching my backlog, then just used the disk from the second Skippa. I did reformat the dodgy one, so I have a second unit ready to go if the current one dies. If that ever happens and it still plays up then at least I'll know the disk is genuinely faulty.