One week equals 14 injections, which makes a lot of needles ... Fortunately the plastic-part can be reused we only need to rinse it with boiling water, but the needles are only being used once as each injection makes them less sharp, meaning it gets more painful.
One would think that the cat might despise you for "sticking it to her" (sorry, bad joke), but she doesn't. She's still as affectionate as ever. Of course she'll try to hide everytime she senses it's "that time of the day" again, but afterwards: no hard feelings.
Good kitty!