Why a Winning System/Method Has to be Rebuilt From Scratch Periodically Interesting, Dave. This is a topic I don't usually discuss. I don't discuss it because I don't really get jazzed about being called a liar when I am telling the truth. lol
Back around the turn of the century (sounding like an old codger here), I was having incredible success with the horses...from a win percentage and ROI perspective. I had a decent job, so I considered what I was doing to be long-term research (it would last forever, right?). So, I was not betting much money... very little. This was back when my state still allowed ADW's. This success went on for a few years, maybe 3 or so. I won't tell the level I was at because nobody would believe me. I will say that I was making at least 60 wagers per month, minimum, so it wasn't like I was just lucky on a few wagers.
Eventually my win percentage dropped about 25% from where it was and my ROI went from unbelievable to a small loss. So, I changed my approach without thinking it through and tanked. Instead of looking for tweaks or even significant tweaks, I leaped into vertical wagers and was not successful.
I believe I have learned a lot. Horse racing is very complex. Millions of factors and that's before cheating or manipulations are considered. I now believe it is good to look at enough factors to be able to ebb and flow, but not more factors than are manageable. But, as you suggest, I have also learned that the Holy Grail is migratory.