I had this 'problem' with my strategies - they'd work for various lengths of time (3-8 months). It was frustrating at first but then I learnt how to figure out when they stopped working early - before I lost all my gains and then moved onto creating a new strategy.
All strategies work until they don't. That doesn't meant to not bother using them, just means keep an eye on them.
I have over 200 strategies that have worked, off and on, over the past 15 years or so. The only one that has worked for longer than a year is this: Buy Home Depot every day except Tuesday near the close and sell it the following trading day about 9:45 Eastern time. This has returned about 20% ROI every year for the past 5 years. You're welcome.
