No Solutions, Like yvilla stated Keep Refilling it / Topping It Off!
The carts design really does not suck themselves totally dry, this may be good though, if you start getting the bad taste you past due on topping off!
You can take a Needle to the wool in the cart to air rate it, may help and is good to do anyways when the wool gets thick and kinda clogged like.
You can also try the "Straw" Trick, May Help A Little, it worked a bit for me. but I just keep topping off my carts all day.
Please Don't Try To Run Your Cart Dry Because You Will Just Toast Your Atomizer...
Yes Check Out SmokingClam Post.
I don't know why your not refilling your carts until their no longer any good to refill, maybe you did not know?
I Think You Should Pick Up Some Juice!
Hope this helps.