That's true. I would recommend a regular charging schedule for such devices rather than waiting for them to complain about the batteries being low. A regular replacement schedule for smoke detector batteries is already a common recommendation from fire departments and insurance companies.
Rechargeable batteries remove the loss aversion associated with ensuring the batteries in a device are fresh, as there's essentially no extra cost to recharging a battery that may still have significant energy in it. Modern NiMH does not develop a permanent memory effect, and rarely even develops a temporary one.
