Lithium-based batteries do not have a "memory effect" like older chemistries. See other threads about battery details, but in short:
- 100% full is 4.2V per cell, 0% dead is 3.0V per cell
- don't run them too low, like below 3.4V per cell , or it will never recharge
- (the Mavic flight battery circuits protect against this but not sure about the controller)
- any time a cell goes above 4.3V it is at risk of a self-combustion chemical fire reaction
- (the Mavic flight battery and controller circuits both protect against this)
- mild warmth and/or slight puffing of the soft pouches after heavy use is normal
- (you don't really get to see this with the DJI battery cartridge designs)
- don't use a battery with visible signs of damage, such as non-trivial denting, rips, cracks or significant puffing
- don't leave them 100% full when moving in and out of hot environments or cold environments
- (the voltage will fluctuate with temperature and adds to the fire risk)
- don't leave them 100% full (4.2V per cell) if you don't plan to use them, adds fire risk
- (the Mavic flight battery circuits will self-drain to a medium load after a few days)
- no matter how well you treat them, lithium chemistry degrades over time and will lose its ability to charge after about 3-5 years
It's probably the last point there that gives people the impression they should discharge every so often. Storage or transport is best at 50%-80% capacity. New products are usually half-charged for this reason.