The problem with most punters is trying to gather the the sample size, for which some members will try to compensate by testing back 12 years.

I've tried to explain that in getting a true POT, in reality you need thousands of bets for a system to properly gauge its performance. So does that mean you would need quite a few 1000 years to achieve that with a system like one with 20 bets per year?

This isn't possible, and so many people report that their system didn't work when it might be a winning system.

Even if you have a system with 50% strike rate the possibility of having 10 losses in a row is very real possibility

Most people tend to launch into a system after it has exhibited great performance, given that a system has a stable line of performance any deviance ABOVE this line will be followed by a deviance BELOW this performance line. SO guess what most people cop when they start ? Yep, the natural deviance to below the performance line to return the system to its normal average performance.

There is no answer to help you gauge the performance of your systems so that you can be absolutely certain, unfortunately!

So stick with your systems, if that is your punting method. For me I test over 5 years into portions because at the end of the day - the horses don't understand all the figures and trainers have change of styles, weights change and jockeys have bad runs. Each to their own and don't get convinced by others your methods are incorrect.