Angelo,
5 years of historical data for either H1 or m15. You can always run a test to see what time frame works best. For example create an EA using 5 years for H1 and use Out of Sample. Then create another EA using 12 years for H1 and use Out of Sample. Compare the two EAs by changing the Data Horizon for the last one or two months.
You can do the same kind of test for m15. Maybe last 5 years and last 3 years.
Alan,
Alan,