The science behind lithium ion batteries is well known and not changing. There is a
great site here which I've seen referenced all over the net and I've not found anything incorrect on it either. Now, there is a lot of miss-information floating around out there, but that doesn't mean anything is changing or we don't know the proper way of taking care of them.
Regarding individual cells there is no advantage to letting their charge drop below any threshold at any time. I believe that may be true for battery packs that report charge remaining and is to calibrate the system, but I am not up on those systems so don't quote me on this