To be blunt the longer you run memory tests the more stable it is, longer being like days as opposed to just a couple of runs. A few years ago, running 10 passes after an overclock or tinkering/tightening with rams would mean you're good if you got no errors in those 10 passes. To add, there have been instances where a memtest or benchmark run went flawless but running an everyday app/game resulted in a BSOD or a reboot, so yeah you need to run a suite of tests to rule out your overclock to be A-OK.
As for the rams, did you make sure your motherboard is on the latest BIOS version prior to performing your overclock? Just as a little point of relevance, please try and include your system's specs to the body of the thread which can aid in adding more meat to the potatoes in the discussion of overclocking. yes I see you have it in your sig space, but sig space specs can and will change over time. When that happens, threads often loose relevance to the person in the same boat as you...hence this question/thread.
Can you list the benchmarks you're running on your system? Ram kit used for the build? Overclock is manual or X.M.P?