How long should it be tested?

The best answer to this question is for as long as your patience allows. Some of our more successful members will paper trade in excess of 6 months before placing any real money bets.

The longer you test, the more the data rules out any anomalies in the strategy.

When you use horse racing, and strategies and systems, you are in it for the long haul, there's no simple wins, no fast way to success, only research, data, theories, testing and trialling to find something that works for you, and your attitude to betting.

So the longer you can paper trade a potential strategy, the more you will find times when it's not so successful, and mitigate these times, creating more profitable strategies.