Average Life of a Power Bank

I have a trick that I use to keep my power banks healthy and ready. I have a Belkin Wemo that I’ve connected a power strip to. The power strip has a bunch of USB chargers plugged into it. Each one has a cable coming off it that I managed with a staple gun and zip ties under my desk. The cables then come up to my desk top where I keep my power banks. I set the Belkin Wemo on a schedule to turn on every few days for an hour and then turn off automatically. This keeps the batteries topped off with out constantly cycling them. If I have a few batteries that are empty, I just simply turn on the Wemo manually and let it charge them for a while and resume the normal on/off schedule. Hope this helps.