should i be looking for strategies for specific regimes or specific strategies that fit specific regimes.

title, ive recently started learning about algotrading / quant trading etc whatever. ive found a strategy that performs realy well in the last 1500 trading days but always falls apart when i test it on history before that, within those 1500 days it performs consistantly and i dont think its overfit, chat gpt has been telling me about how its specialized for that specific regime and that i should have a portfolio of strategies all fitting different regimes, so would the next step be to look for strategies that work well in the period before those last 1500 trading days. is it actualy unrealistic to look for a strategy that performs well consistantly throughout lets say a ten year period / through all different regime types

sorry if these are stupid / obvious questions, thanks for the help.