How long will the V20 last?

[Mooncatt]

With a properly-set charge controller it doesn't materially hurt the battery to leave it plugged in all the time when not in use. The problem is that there's no phone made that has said properly-set controller in it.

It's not the charging that hurts a battery. All chargers kill the charge when a battery is full. It's the mere fact of keeping the battery above 75% that hurts it long term. You could charge it full, completely disconnect the battery and leave it on a shelf, and it'll still degrade quicker than a partially charged battery. That is why they are shipped with a partial charge in the first place, aka a storage charge. It's to limit the degradation while sitting on the warehouse shelf for who knows how long before use. I'd have to go dig up the article again, but Battery University found in their testing that the best long term lithium charging habit is to basically keep the battery between 60-75% (that's not taking into account other factors like personal usage needs).

As for the capacity issue, I think manufacturers could double their capacities and users will still complain that battery life between charges is too short. It's a never ending complaint I see everywhere. Give them an all day battery, and they will complain they can't go 2 days. Also, performance has increased more than battery capacities. You can't expect a phone to do something like run console quality game graphics all day and still have a fantastic battery life.