If a system is not proving profitable and not providing desired results then I definitely consider tweaking it. We all know that as the market evolves, a particular system may become obsolete and it needs modifications to retain the effectiveness in the market.
I give up my old system when I feel that it is no longer in sync with the market. I am not one of those kinds of traders who leave the old system and adopt a completely new one. Rather, I prefer to make necessary changes in the system that I was already using.
The tweaking frequency has indeed increased as the market is evolving faster due to automation over the years. We need to constantly adapt to change.