"Memtest86 continues executes indefinitely. The pass counter increments each time that all of the selected tests have been run. Generally a single pass is sufficient to catch all but the most obscure errors. However, for complete confidence when intermittent errors are suspected testing for a longer period is advised."
Bugger... does that mean for the past 49 odd passes I've been wasting my time, and that this stick is in fact perfectly fine?