I buy Milwaukee and Ryobi power tools because they have Samsung Li batteries inside their battery packs.
If I am actively using them I will charge them up to 100% but I always run them down below the 75% level when I know the battery is going to sit overnight or longer.
I would like to apply your idea.
I only have 1 Milwaukee tool (I have yet to use) and no Ryobi's.
How do you know that it is at 75%?
Is there a monitor on the charger or do you know from experience on how to judge it?