These longer TF strategies would need to work over months and years
No they don’t. Just because you are using a daily chart does not mean you have to be in the market for months. You can be in for seconds if your stop and limit orders and the market decides that that is what is going to happen.
The danger of your idea of testing on only recent data is that you have no idea how your strategy will behave when the market changes and you can only tell that the market has changed once some time has passed by and you have some data to show you that it has changed. By then your strategy has drained your account.
Markets really only do three things – they go up, they go down or they go sideways and today’s candle could be the last one in any of those market structures and you will never know that until it is too late.
Trending/momentum strategies only work in two of the market types whereas mean reversal can be made to work in all three – in fact it absolutely loves a sideways market. Just my humble opinion.
