A discharge cycle is just measured in % percentages, meaning if you discharge(I.e. use your laptop) for one hour and in that time you discharged 20%, then sat it back up to charge back to 100%, it would then take 5 days to complete a discharge cycle of 100%., assuming you only use 20% each day.
Bear in mind, a battery takes "damage", no let's call it wear instead, during charging, think of a piece of wood getting compressed to hold energy, at some point the wood fibers will have become so weak from the repeated compression, that it will just collapse and fail.
And yes, Lithium Ion/Polymer batteries will wear down faster if they remain in the charger after reaching 100%, be it phones or laptops, since they don't come with a 100% shut off capability, meaning the charge will NOT stop completely.