Thanks for the update Louie!
I have thought about using converters but I feel like they do give a tight fit, you would be back flushing your nib and feed every time you changed inks etc. I am open to hearing how great they are but my perception is that convertors would be kind of a hassle? Please correct me if I am wrong!!!
Keith -
I've been using fountain pens exclusively for more than 30 years, and for most of that time, I've used converters. In fact, of the pens that are currently on my desk, inked and ready to go, only one has a cartridge, and it's a special case (it's body is too short to accommodate a converter). So admittedly I bring a strong prejudice to this issue.
In my mind, the main advantage of cartridges is that if you are traveling, cartridges are far more transportable than bottles of ink. Before I retired, I traveled extensively for work, and a trip that lasted more than a week inevitably became a problem because of the risk that a single converter wouldn't hold enough ink, and shlepping a bottle of ink is a real PITA, especially with suspicious airline security people. My solution was to take several pens, but that also caused the security screeners to wonder about me. Of course, my wife wonders about me also, but that's another matter.
If you are simply refilling the converter, you have a choice of leaving it attached to the nib/feed and drawing the new ink through those components, or else removing the converter and filling it directly. Most people draw the fresh ink through the nib/feed. There are three reasons for this. One is that drawing fresh ink through the nib/feed assures that they are primed with ink and ready to start writing immediately. Another is that drawing fresh ink through the feed will dissolve any dried ink inside the feed. Thirdly, on most pens, the fit between a converter and the pen section is a friction fit (there are a few pens that use screw-on converters), and frequently removing it increases the risk that it could become damaged and need to be replaced. Unless you are changing color or ink, there is no need to flush everything with water as part of every refill, especially if you write a lot and have to refill frequently. That said, its not a bad idea to do an actual flush with plain water every three or four refills.
If you are actually changing ink, you definitely want to flush the nib and feed regardless of whether you are using a cartridge or a converter. This is true if you are changing colors (some fountain pen uses intentionally mix inks, but that's an arcane science, not something you want to do inadvertently as part of a refill), and its critical if you are switching to a different kind of ink that might be incompatible with the ink you have been using. In fact, a converter makes that easy because, as it's alternate name implies, it can function as a pump to force clean water through the nib and feed. If you don't have a converter, you either have to soak the nib and feed in water, or else use a pipette or ear syringe to force plain water through those components.