The 250 cycle rating is if you draw 15amps continuous from 4.2v down to 2.5v. Doing this causes the cell to get really hot. This is why the life is short.
My pack is 14s14p and I foil at an average amp draw of 30a. So, 30 ÷ 14 = 2.14amps per cell. My pack barely even gets warm.
If you keep the load per cell low these cells will last 1000s of cycles with minimal reduction in capacity.
It’s amazing this cell can handle 250 cycles at a 15a continuous draw considering the cell gets up to it’s 250 cycle rated temp of 140°F (60°F).
I tested the cells at 10a continuous discharge and they got too hot to touch, but well within the manufacturer specifications. It is this heat that limits cycle life. Run your cells where they stay cool and they will last forever (1000s of cycles).
My battery build: