I get what you're saying, but this goes against the guiding principle that was hammered into me when I first got interested in EV's, which was to charge whenever and wherever you can, so that you're always prepared for the unexpected. It's also not at all 'consumer friendly'. I fully charge my phone every night, overnight, and I fully charge my iPad every few days, as required. If I only charged it to 20% each day to cover my average usage, that might extend the battery life, but it would be super inconvenient. As a regular consumer (i.e. not an early adoptor,or someone that really cares whether is gas of electrons that make the car move), I'd want a simple rule of thumb, that's not inconvenient, otherwise I just won't do it.
Right now, I charge twice a week, and that works well for me, but I'm still not sure if that's good for the battery, bad for it, or neutral, since my average SOC is probably about 50% across the week.