I'm a cautious person. If you can over-clock and still keep the components within their maximum specified acceptable voltages, that's where I stop.
Visit the web site for your processor manufacturer -- did you say it was an AMD? There should be a table of processors which specifies the maximum rated voltage for the processor core.
My inclination is that anything over that voltage, and the greater the difference the greater the risk -- is riskier.
Until about a year and a half ago -- spring 2003 - I had a Gateway Pentium 166 still running with a string of hard disks totalling about 15 GB. It had been a proxy server in 2000, then from 2001 onward it was just a file server. So, as I said, I retired it in 2003, modded the lovely full-tower case into a fully-compliant ATX form-factor, and it is now a 3.0C @ 3.75 Ghz.
What I mean is -- it lasted that long, just like the assertions of a ten-year life-span for processors said it would.
The problem with going outside rated specs is that you can never anticipate just exactly when the lightbulb will burn out. So even if you plan to dump the machine in a couple years, worrying about reliability and the integrity (and continued life) of your data means attention to a backup schedule.