Never and Never. Only when a goal has been reached and I am entering a new time goal time period.
I dont like these kind of graduated money management systems. Why? because they are all weighted so that streaks can kill you. Lets take an example:
Lets say you go 60% for the first 6 weeks of the season betting 10 games per week (60-40). So you start with a 10K bankroll, and it has now become 15k using your betting strategy going in to week 7.
Now, in week 7, I go 0-10. You lose 5,250.
So - what you have done - is gone 60-50 (54.5%) for the year and you are down money.
It works the opposite way too. If you lose a bunch of weeks in a row, it takes you much longer to get even overall because you are betting much less.
There is no statistical advantage to betting this way and while it may increase your ENTERTAINMENT value by making you last longer in the season - it does nothing good for your financial bottom line.
In conclusion - IT IS MY OPINION - that there is no compelling reason to employ any kind of graduated wagering system - and it is FACT that it has no mathematical EV advantage.