How long till the law of large numbers is in play?

How many times does an event need to be repeated for the law of large numbers to play out?

only once if it is a large number to start with....

LOL... cute, but what you need is something called a "confidence interval" or "confidence level" which is how many times until you're confident in the statistical play out.

First it depends on how confident you want to be. But math and long story made short... 50 to 100 trials. That's why a 2% risk percentage is important, if you're trading too much risk you might get knocked out on a huge run against you that later regresses to the mean.

This is all good and fine IF you actually let your trades play out till the end. The simple fact of it thatr I realized is that if you take profits on trailing stops or manually close trades before the target TP many times but you don't move your SL ussualy, and your SL to TP ratio is say 1, then you can loose in the long term even if you were right about most of your trades, because you took less profit and greater losses. That's why I'm now only entering trades when the SL to TP ratio is at least 2 - which doesn't mean I always wait for the full TP because I put a TS at half or a third of TP size and occasionaly just close it manually. These trades are not easy to find and are relatively rare, but I believe it should work out well in the longer term. Testing

Nod. It's not just the expectancy rate, it's also the risk to return. You could have a 40% success rate but if you're working at 2:1 or 3:1 returns you'd still turn a profit.

All of that is well and good, but in real-time it takes a lot of discipline to let trades play out... over and over, whether profitable or not.

Indeed, psychology and method of handling profit and loss during the trade is at least as important as knowing where and when to enter it.