The self-tuning just remembers previous best-fit data, that's all. If you factory-reset the ECU, for example, it has to go back to baseline and then figure out the best spark timing numbers to use given your fuel quality, air density, ambient/coolant temps, etc based on sensor feedback. Once it homes in on the correct values though, you can shut the car off and start it back up the next day and it will be much closer to optimal right off the bat (well, assuming you didn't ship it to another continent with different weather while it was shut off
). Reset the ECU and you're back to square one again.
But people get confused about this. They know the ECU is somewhat adaptable, and they see some effects where hard-vs-soft driving styles lead to a semi-persistent effect when you switch drivers for a few minutes, etc. They start thinking the ECU can really "learn" your driving style, as if it has some internal parameter that goes from 0-100 and measures "how aggressive this dude likes to run the car". It doesn't,
AFAIK. It's just adapting to current conditions, and it will re-adapt within minutes if you change the conditions drastically.