i also do 5 between overclocks, but run it slightly different.
i use custom ram as i find its tests it better.
open task manager, see how much free ram is listed under the performance tab, this way u are not using chached ram.
if i have 3800 free, then i will enter an amount just below it, so 3700.
then select 2 or 4 threads or how many cores your cpu has.
thats it, ideally your ram will be using more than 75% in IBT,
dont use pc while running test