I would like to know what advice to give the consumer about how often they should charge the device.
So running the battery down is bad, but there's a limited number of times that the user can put it on the charger to keep it charged up.
How much of a charge would you need in order to justify the wear on the MicroUSB port that happens when you plug it in or unplug it.
Let's assume that neither the Li-Ion battery, nor the MicroUSB port is serviceable by the end-user/consumer, and when either one fails, the device must be sent in for repair.
The device I have in mind in this case is a cell phone, however (I would assume that) this concept should apply to any device that uses a MicroUSB port and a Li-Ion battery. If this assumption is wrong, please help me (and others) to understand why.
As @Asmyldof points out, for very light usage, it can be fine to plug the device in once or twice a day and never run out of "plug cycles," but as smartphones begin to fill roles that once were reserved for dedicated hardware devices, this can quickly change.
Think about a delivery driver who gets in and our of their car 20+ times a day, and has to keep their phone both charged and on their person so they can be reachable by the dispatcher (and maybe they need to use the GPS or listen to Pandora too.)
At 20 cycles a day, that gives you only 1.3 years of life for the port. That even assumes that each of those 10,000 cycles includes a plug-in, and an un-plug.
Then there are those who like to set their phone on a non-wireless cradle charger to prop it up and keep the screen on, then take it off each time they need to answer a call or reply to a text. The consumer may not even know that they are drastically reducing the life of the device itself in their good-faith efforts to preserve the battery.
There must be a "happy medium" somewhere inbetween where both of these components will wear uniformly, and neither one causes premature failure of the entire device.