Most tool batteries do not die of old age or of being used too much. They die of heat, and almost all of that heat is avoidable.
The single worst habit is leaving packs in a vehicle. A van cab in Nairobi sun regularly exceeds 60°C, and sustained exposure at that temperature degrades cell capacity permanently. Packs stored this way typically lose a third of their capacity inside eighteen months.
Second: charging a pack that is still hot from the tool. Most modern chargers will wait, but not all do. Give a pack fifteen minutes to cool before it goes on charge.
Third: storing packs fully discharged. Lithium cells sitting at very low voltage for months can drop below the point where the protection circuit will allow a recharge, at which point the pack is scrap. Store at roughly half charge if a pack is going into a drawer for a season.
Fourth, and easiest: rotate your packs. Using one battery for everything while a second sits on the shelf ages the first at double the rate and does the second no favours either.
