Good reference, thanks. Notice, please, two things of import to us (remember it's written mostly from a laptop POV). First off:
"Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The shorter the discharge (low DoD), the longer the battery will last."
This says to me 'never deep discharging is better than doing so'.
Also notice things like:
"Most Li-ions are charged to 4.20V/cell and every reduction of 0.10V/cell is said to double cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.00V/cell should deliver 1,200–2,000 and 3.90V/cell 2,400–4,000 cycles. Table 4 summarizes these results. The values are estimate and depend on the type of li-ion-ion battery."
and
"Tables 2, 3 and 4 look at cycle life as a function of discharge, temperature and charge level."
Those tables, much as some have trouble following such data, have great insight if you study them a bit I think.
I continue to believe the two best things you can do to prolong the battery service life are to limit (or better yet avoid completely) deep discharges and not fully charge. Doing so should let you double, triple or more the lifespan. Keeping them cool is good too, but mostly past our control here.
In the end they will die if nothing else in the vape does first. No need to rush that, and hopefully the replacement will be easy and cheap when the time comes.
OF