I've got two that have been modded. They run for about a week then I lose a board. I turn it off and then on and it comes back for about a week. If you're hosting them at home and keep an eye on them, then it's not much of a problem. This happens only to the modded ones though.
That is not exactly true. Both of my units are unmodded and they only last between 7 and 14 days before requiring a restart due to a board dropout.