Simple mathematics suggestion.

I am a bit long in the tooth for solving simple equations as it was 50+ years ago since I was at university.
It would be very interseting if someone were to produce an equation for the most effective removal of money from the loan programme. It could be in the form of a family of graphs or simply a more complex equation where the variable is the time in months for the total length of ROL removal to withdraw, where you decide the number of months.

eg:- 40% withdraw ongoing roughly equates to a constant.
50% gives a slight increase.
60% gives a noticeable increase.
and so on------

50% would eventually overtake 40% but be less at first.
60% would eventually overtake 50% and so on------

A mathematical formula is therefore required if we have
an able mathematician amongst us. Please advise.