It's very unlikely that you'd get three hundred charge cycles with this ever-cheapening chemistry.
Lithium-*
batteries don't have a memory (practically / over the expected service-life of these
batteries). You can use them anywhere in the charge cycle.
Lithium-Ion hates being deep-cycled. You're better off not discharging them to the cutoff before recharging them.
In theory, you can leave them on the charger. That's assuming the charger is really doing the "right thing". I'm not entirely convinced that it is, but close enough as to make no difference really. Mine stay on the charger all night.
These are extremely cheap
batteries, and incredibly disposable. Just plan on replacing them every couple/few months and call it "good".