Lithium ion batteries, such as those in laptops, don't degrade based on charge/discharge cycles the way that older generations (NiCd, NiMH etc) did, but rather

Lithium ion batteries, such as those in laptops, don't degrade based on charge/discharge cycles the way that older generations (NiCd, NiMH etc) did, but rather lose permanent capacity mostly as a function of time and temperature (although discharging below 20% or so exacerbates this).