Modern batteries have life estimates based on charge cycles. Charge cycles are defined as full discharge followed by full charge (or vice versa.) A half discharged battery being charged to full again counts as half a charge cycle. So it doesn't matter.
In the past, there was a problem with "battery memory" and this could be remedied somewhat by discharging and charging in certain patterns. The batteries used in Apple's products don't have the battery memory, but all rechargeable batteries degrade with use.
Again, it doesn't matter. Charge it how and when you please.