Say as you wish, however, as mentioned, we specialize in producing all types (SLA, NiCad and Lithium) mainship and e-batt batteries for aircraft, commercial and military and I can assure you that lithium's will loose capacity faster if discharged "deeply" than if they are kept topped.
How much "faster" is hard to say. They have a certain number of discharge/charge cycles during their life time. Deeply discharging and then charging counts as a charge cycle. "Deeply" depends a little on the particular lithium chemistry as there are several in use now.
I never said that they can be discharged "too much", I said that deep discharging and then charging will shorten their capacity faster than keeping them topped. As an aside, for "long term" storage they should only have about a 50% charge. This is why the cellphones (when new) have their battery only charged about 1/2 way, if anyone has noticed.
And this is not something I "heard" on the internet. This is from a engineer with over 40 years experience in the field (me).

Fred