I usually run Folding@Home for 8 hours straight for CPU testing. Prime95 has also been a good choice for me as well. For memory testing, I boot off a Memtest86+ disk and run it overnight.
memtest and prime should only stay at the labs. For benchmarking or gaming oc your cpu to the max stable (with a good cooling) and you'll be allset . For office, surfing etc. just use stock speed.