How often do I have to charge my Apple Pencil Gen 2

The need to recharge your Pencil is determined by its frequency of usage - and how it is stored when unused.

Your second generation Pencil should be docked with the host iPad whenever the Pencil is not being actively used - as this will optimally charge and maintain the tiny Pencil battery. Whilst a fully charged Pencil can be safely stored for many days, be aware that the built-in accelerometer will “wake” the Pencil’s electronics wherever it detects movement - slowly depleting the battery. Keeping the battery docked with the iPad protects the battery and maximises both battery life and longevity.

Setting aside a Pencil when unused is a recipe for premature battery battery failure. If the Pencil battery fails, the only remedy is replacement of the Pencil.