Ink cartridge refilling questions

[quietglow]

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I just happened into a large stash of Ilford Gallerie papers. I tend to print frequently anyway, but that frequency is now likely to go up. I've been debating refilling carts for a couple years, and this is now making it even more desirable. I use a Canon Pixma Pro 10, which uses pigment inks. A couple of questions for those who do:

1. I am inclined to go with Precision Inks, as they seem particularly aware of the fineries of color matching (they will only supply the OEMs red in their kits as they can't get a perfect match for it etc). Has anyone used them and found they like another source? (Ink Owl would be my second pick).

2. I saw mentioned somewhere that instead of replacing/refilling individual carts as they are empty, it's best to have a second set of carts and replace them all at once each time a single cart goes empty. I can't find the source I read this from, and I don't understand the reasoning. If anyone does this and can tell me why it's better, I would love to hear the reason. 

Anything else that I ought to be aware of, please let me know.

Thanks!