3-5 drops in dry cart stuffing won't go far because there is nothing to keep it from just spreading elsewhere in the stuffing. A cart wicks best for me when around 1/2 full and and topped off on top. That way the juice below feeds up through the stuffing and keep the top damp helps them do that. After a few days I threw out the white cart stuffing and cut blue foam instead which is a more consistent density and wicks well for me. On a full fill I pull out the foam stuffing, fill the cart 1/2 way, put the foam back in and push it into the juice to wet it, reposition the top edge of the foam at the top edge of the cart, and top off with 1-3 drops (depending on the size of the cart and what it needs to look damp on top). After doing that, then I can can just top off as needed until topping off isn't helping and that usually means the foam stuffing is totally dry.
I mostly use cartos now instead. They can be kept damp pretty well, hold more juice, and need juice added less often.