That's not how it works. If the system encounters an instability that you are unaware of it's possible that damage/corruption could rear its ugly head weeks or months later!
You do want to heavily stress using LinX finding the memory amount that produces the highest throughput (in GFLOPS) and select the amount of time to run. I suggest 300 minutes - 5 hours as start. Forget this 20 passes = stable nonsense. Alternatively you can install BOINC client and register for a project and allow it to crunch for 1-2 weeks. If you don't see computational errors in that time period (or system crashes) it's a pretty good bet it's stable enough for most (non critical) tasks. If you were doing the latter overclocking wouldn't even be on the table of consideration. (along with non ECC ram, etc.)