Once again a few factors can effect the lifespan of your power banks.
Extreme Temperatures – Very hot or cold temperatures will drain the power out of a unit quickly. This will cause you to recharge the unit more frequently thus reducing the power banks lifespan.
Ventilation – This applies to the first factor of temperature. When units are charging or recharging a device they can become quite warm, be sure to have them in a well-ventilated area while in use.
Keep Power Banks Topped Up – It is a wise practice to top up your power banks during the offseason when they are not in use. Common practice is to top up the unit once every 2 – 3 months.
Power Banks are much similar to batteries found in boats and cars. They only have a certain amount of cycles before they become depleted and need to be replaced. A unit that is not used very often can last many years if kept topped up and stored in an ideal location.
As mentioned briefly above the 20/80 method should be applied not only to your devices but to power banks themselves. Although you should charge power banks to 100% after being in use it is wise to not let them drop below 20% or run them completely out of power. It takes a lot of time and energy to get the charge of the unit back up from below 10% and is hard on the unit.