I bought a
second hand Pro-300 2 years ago. I don't use it that often and have probably done about 100 A3 prints on it in that time. I mostly do them in batches of about 8-10 at a time, as the printer does go through an "ink adjustment" cycle if it's not been switched on/used for a while. The print quality is much better than the cheapest DSCL prints, but it does take a bit of fine tuning to get the results perfect. Mostly I have to increase the brightness in the Canon print plug in for LR/PS by about 15-18% to match what I get on my screen.
I've gone through at least 2 of each of the 10 print cartridges in that time, and maybe 3 or 4 of the photo black and CO as I do a lot of black and white prints. All in probably about £300 in inks, and about £150 on various boxes of papers. That works out at about £4.50 per A3 print which is higher than I thought it would be, but a lot of the early prints I do would do one or two, re-print if required and then leave it for weeks or longer before starting it up again. Hence the ink usage is much higher than if I had had started doing them in batches.
I don't change the ink on the first warning about low levels, but instead when it tells me it's run out - generally about 2 A3 prints later. If I've got any other inks that are on low warning levels, or close to it, I'll swap them out at the same time, as the printer goes through an ink adjustment cycle when you replace a cartridge which will likely nudge the one running out over the edge. I've got a couple that weren't quite empty that I've resealed and keeping for emergency use.
I've left mine switched off for 4-5 months at a time and haven't had any issues with blocked ink jets/heads etc. It does take about 5 minutes to start up and do all it's adjustments after an extended off period though.
I would have likely saved money by sending off the prints to a photo lab, even when choosing some fine art papers, but as always you spot things you would like to change in a photo once you get it printed and view it under good lighting, and the ability to make the changes and re-print within minutes is ideal, rather than waiting days for your prints to arrive before spotting some mistakes.
I successfully achieved CPAGB last year using my own prints and mounts, and I enjoyed the steep learning process about the whole printing process, paper profiles, the impact different papers have on the final image etc.