We've got two digiboxes, both Pace, one a SkyPlus box, the other an 'ordinary' one which must be well over seven years old -we've had it for so long we can't remember when we got it -and it works OK. The 'newer' one is four years old and up to now (fingers crossed) has also been problem-free.
So unless we've been lucky, I'd say age isn't a problem.