Ever since I got my 2200 about 10 years ago, I've changed the carts in the middle of a print with no problems. Even today the 2200 runs out in the middle of a print and you can't tell that it ran out of ink in the middle of the print. Even has happened with two and three carts at the same time...
Since then, I've experienced the same with my 4000, 7600 and 9800 and the prints are just fine. Just use it until you run out and then change the cart.
A couple of years ago, I had a print run of 700 24x18 prints on the 7600. 28 carts and ten days later, the prints looked as good as the first ones of the run, even the ones that had cart changes in the middle of the print. The client was happy and the check had lots of zeros...