How Long Does Fountain Pen Ink Cartridges Last
Q:
How long does a fountain pen ink cartridge last?A:

Fountain pens come with nibs of varied sizes. This is a personal preference and different size nibs are created for different tasks. Extra fine or fine nibs lay down a thin line and will therefore use less fountain pen ink. Wider nibs such as a broad, stub or italic nib are created to write a wider line with more line variation. Line variation is the thickness of the line a fountain pen writes vertically opposed to horizontally. A music nib would also use more ink as it has two breather holes with a second ink channel.
The next item to consider is the size of the ink cartridge. Larger cartridges obviously hold more ink. Some ink cartridges are longer, such as the Monteverde Magnum ink cartridge or the Edelstein ink cartridge, but will not fill all pens.
The last factor is the ink and the paper you use. Some inks may be thinner or flow faster. Faster flowing inks will not last as long. The same holds true for the paper used. Some papers absorb ink faster than others and therefore as you write you use more ink.
I know this doesn't definitely answer the question but the length of time a fountain pen ink cartridge will last is subjective to many factors. Best case is you will get a feel for how often you replace your ink as you use the fountain pen. If you are looking for better "mileage" consider using a converter or a piston style fountain pen that will hold more ink than a standard ink cartridge.