I base my min off the original capacity of the cell. So if Im using new 1800s (like reclaimed replacment batteries) ill use 1800, but if they are say samsung 30b (3000mAh) then 2100-2200. I find that if its below 70% of the original the cells start to get a bit wiggy.
I have to call back to my original post, dont do arbitrary capacity minimums, have a % of original design capacity as your minimum.
A 2100mAh minimum on first a cell that was 3400mAh compared to a cell that was originally 2400mAh are two entirely different beasts.
By design, manufacturers slate 70% of original as their 'throw away' point. Im inclined to be more optimistic on cells that started at higher capacities.
The long and short is its a good idea to test what different cells do.
Lastly, remember that capacity also affects the C rates for charge and discharge, so as a cell declines you need to account for changes in tolerances to stop the cells 'falling off the edge' quicker.