Cache cards die like anything else. I have a (now infamous on this board) IIci that runs NetBSD, which I use for internal DNS and some other menial tasks appropriate for an '030. About every three years it throws a kernel panic, and refuses to boot. Invariably when I investigate the cache card has blown, either bad caps or something else, and replacing the cache card fixes it. Look to see if you've got cap yack on the PCB, or some other possibly correctable fault. So far it's chewed through three in its almost 10-year service lifetime with me, and probably more when it was on someone's desk.
Meanwhile I have built up a stockpile of IIci cache cards thanks to folks here and others. So my cache-card-chewing IIci will live for a number of years yet, which is good, because it does its job very well most of the time.