I have noticed that with all my wacko systems I have concocted over the years that the length of time required to test the system is inversely proportional to the average odds of your runners.
Thus if you have a system following odds on runners I believe a shorter sample will be quite indicative of future results. Conversely the longer priced investments will require far longer trial periods.
Just my observation.

__________________
"Not winning on a horse that came first is one thing.....Losing on a horse that didn't come first is something else entirely!!!"