The research is all over the road on this. The latest out there is to charge to 100% as often as you can. The 100% will decrease with every time you charge but that decrease will be smaller the more often you recharge, until the technology on these batteries changes we are stuck with this.
As it turns out, I have to charge mine both ways to keep going all day, lol I start with a full charge in the morning, and recharge them at lunchtime even though they haven't run all the way down yet. If I don't do that, I run out before I get home in the evening, and I really want them for television. So then after lunch, I put them back on and run them most of the way, if not all the way down until bedtime, when I charge them fully overnight. I'm seriously thinking of buying another set so I can run it down all the way at any given point and still have a charged set to use while the first one is recharging.