I would say the following are pretty certain:
Cell properties that dictate battery properties:
Lithium cells like room temperature.
Higher temperature can allow the cells to be pushed harder, but temperature needs to be controlled.
At very low temperatures and at high SOC, (around 4.2v for many lithium technologies) there is a tendency for lithium metal to form inside the cells, effectively shorting out the cell from the inside of the cell.
Even when used under optimal conditions, lithium cells have a predictable degradation based on energy throughput.
Properties of battery (being made up of cells):
In reading any posts about batteries, talk of 'cell' could mean one single cell - like one aaa or aa cell, but is more likely to refer to what might be better called a 'super cell' (brick) that is made up of many cells wired in parallel that still behave like a single cell.
When you wire multiple cells (or super cells) in series (to increase the voltage) you unavoidably have the issue of not all cells / super cells having identical characteristics - however closely you try to match them.
Inevitable slight mis-matching between supercells (or inevitable occasional cell going bad) means that supercells will charge and discharge by slightly different amounts / speeds which becomes self-amplifying. ie: imbalance leads to greater imbalance. It is therefore essential to have a charging mechanism that keeps fixing any imbalance either instantaneously during charging (which I don't see how is possible but I am still looking for evidence) or more normally as you near completion of charge to a preset (max) level, you allow cells to absorb energy at a fixed voltage and reducing current self-dictated by each supercell. Eventually, given time, all the supercells should end up at very nearly the same voltage (SOC) - ie: balanced.
High currents through the series-connected cells either charging or discharging either add or remove energy from the supercells at slightly different rates, dictated by the intrinsic and inevitable slight mismatching. At extreme levels of charge or discharge, it is possible that some supercells are charged or exhausted to their limit while others still have a little capacity remaining. To get at that remaining capacity increases the potential of damage to the supercells already at their limits. Best policy is to avoid running the battery near to these extremes.
These are not Tesla specific, so they apply to all Ev's. Tesla already do a lot to try and both protect and optimise their batteries compared with other manufacturers, but there are always trade-offs. In the case of Tesla, this incudes not allowing regen braking when it could damage the battery (cold / high SOC - actually Tesla seem to focus mainly on low temps). They also 'waste' or at least use energy (but hopefully in a useful way) to heat the battery when that could be beneficial, and also to cool for the same reason.
So some of the conflicting info we read is I believe because of the conflicting demands placed on the batteries. But by adjusting use where convenient to take the above into account, you should extend the useful life of the battery.
Any one who disagrees with the above might be kind enough to post their reason and supporting evidence!
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