Wow! TWSBI holds ink like a Duracell battery lasts! I am only now getting low on ink Iroshizuku Kon-Peki. Filled this pen last Thursday. I still have several more pages to go before needing to flush & fill with another color. Do you use this as your workhorse writing instrument? Or do you not fill this pen to capacity? Or is this pen the one you routinely load ink into and let it flow? Inquiring new TWSBI 580 owner's mind wants to know.