I have multiple intraday strategies that backtest well under certain timeperiods from now to one year or more in the past.
For example, I have one that trades quite often with a profit factor over 2. It does great for the last six months but falls apart if you go much before then. I have another strategy with a profit factor over 3 that works for a year in the past but then dies beyond that. These are both high accuracy backtested with commisions and slippage included.
My question is, how long do strategies last nowadays and if intraday quant strategies are mostly fighting each other, are they rapidly changing market behaviors because all the quant firms are in an arms race against each other?
I might be working too hard to try to find some holy grail intraday strategy that backtests with amazing results for the past 10 years, when the expectation should be to be constantly adjusting a strategy.