not sure about buying systems but a tip for one you have made is to.
1) calculate its average drawdown.
2) note its maximum drawdown.
3) note a performance figure that is a minimum.
Dont start trading it until you are around 1).
Stop trading it if 2) or 3) are breached by some margin.
So for example one intraday strategy I am waiting to trade has the following characteristics:
1) 5-15%
2) 20%
3) minimum net profit per year 20%
So I am waiting for 1) to happen (which is a bugger because it has been performing well recently !).
And I know when to stop and reevaluate - when it loses > 20% or returns less than 20% in a year.
By the way always think about statistical significance when you are backtesting. In simple terms it is laughable that some "serious" system developers/resellers that post on this board show systems that have been backtested on sub 100 trades. I am constantly a victim of curve fitting even if I have tested it on over 1000 trades.
Funster
