Usually not — a modern lithium tool stops drawing current when it is full, which is why charging stands exist at all. What ages a cell is heat and sitting at full in a warm room, not being plugged in.
Three things are worth separating here, because they get run together.
Being connected is not the same as being charged. A lithium charging circuit tapers off and stops when the cell reaches full. A tool left on a stand is not being force-fed current for eight hours; it is sitting there having finished. This is a general property of the chemistry and the circuit, not a claim about one product.
What does age a cell is time at a high state of charge, especially warm. A tool permanently at 100% in a steamy bathroom ages faster than the same tool used and topped up. The effect is gradual and small compared with the thing people actually do, which is the opposite extreme — see below.
And the real mistake is the other one. A tool left flat for months is worse off than a tool left on a stand for months. Deep discharge over long periods is harder on a lithium cell than a full charge is, and it is the failure mode that kills a spare trimmer in a drawer.
What is published, as opposed to general: the Philips S7887 is the only product on this site that ships with a charging stand, which is a maker designing the tool to live plugged in. The rest ship a cable. Where a manual advises against permanent connection, that instruction is about that circuit and it is the one to follow.
Two neighbors to this question: whether charging overnight specifically hurts, and whether to run the cell flat first — which it does not.
Check your own manual before you follow anything here. Temperatures, water ratings and supply voltages differ from model to model, and the maker’s own figures take precedence over anything written on this site. A supply of the wrong voltage is a failure rather than a slow charge, and the figure is printed on the tool — not inferred from a connector that happens to fit.
Last reviewed October 10, 2026