2-5 years! son of a B**** - wow... I'm sorry, :/ I thought they'd be better than that by now.
Even 8-10 with recharging isn't brilliant... but I suppose new tech for internal applications is slow to trickle into the mainstream ('elf and safety etc...)
Ho hum, at least it's better than yearly, that really would be a pain in the .... er... yeah... [gets coat]