So I realize the batteries on these are not user replaceable. I know laptop batteries have issues of possibly only lasting a year, at which time you would need to have it plugged in all the time or replace the battery. Our non-profit is considering implementing these in our group homes. They would be used daily, and without being plugged in. They would be plugging in every night for charging. What we need to know is how long would these units last being used like that? Would the battery be able to hold a charge after a couple of years? After 5 years? I haven't read this figure any where, we're just looking for what the manufactures are expecting.