Hubikote have been sending out some spray fresheners to "recharge" those short lived card ones from Waxybox, so try spraying some onto the card if/when it's dead.
I found my Hubikote one lasted about 2/3 days, in comparison the Nanolex one that replaced it the day the Waxybox arrived is still going strong at the moment.
Okay, that's enough of this terribly exciting air-freshener talk for now.