I don't think this is the case, over the last 15 years or so I've had a Pentium 60 running at 66MHz, P150 running at 187MHz, Celeron 300A at 464MHz, AMD TBird 1GHz at 1.4GHz, P4Northwood 2.8 at 3.2GHz, an E4300 1.8 at 3.4GHz...
All machines overclocked as far as they remained stable without doing anything really exotic, all machines run for at least 2 years, some 5 years+. I've never experienced any kind of shortened life. In fact the only computer components that have ever failed on me have been a couple of hard drivers a few years ago.
My rule of thumb is that if it's stable it's fine.