If I set it to 4 years, it gives me 1 unit per day, but maybe that should mean that 1 unit is the minimum, but I can do 2 units if I'd like (i.e. 2 year pace), then pace slider would "lock" at that the end of the second unit.
Or, just have a "max review cards" setting in my study settings, then let me study more than my minimum daily assignment up to a certain threshold of flashcard reviews that I'll have the next day.
If my flashcard reviews is set to "Max 100," for example, I can study more than 1 unit, but I can't study so many units that I would have 101 flashcard reviews due the next day.