I got my Epson 4000 when it took six months for delivery back about 2003-2004. I still use it for sheet fed printing and keep it going since the print quality is still fine after all these years.
I do let it sit from a few days to a few weeks when I'm on the road. I simply turn it off. My studio is partially in the ground. It gets cold in the winter and warm in the summer. When I'm working, I simply try to keep it comfortable which in the summer means running a fan and open windows and when it's too warm, going out and shooting. In the winter, I run the heater to keep the edge off the cold. Luckily, it doesn't freeze inside here!
Sometimes I'm lucky and it prints fine after sitting a while, other times, I've got to run a bunch of cleaning cycles before it gets going. So far, it still works and prints just fine. If I'm lucky, it takes just a couple of cycles, other times, takes it will take a couple of sheets. The last time I simply added a wet paper towel under the head and let it soak a little which also helped to clean the ink off the head and the printer head path at the same time. That did the job, along with replacing a cart that was just a little bit too old and didn't have too much ink left...
Since I also have a 7600, when the ink runs out, I simply swap out the carts.
BTW, you aren't limited to simply 110 ml carts, 220 work just fine and I've been using them for years. They just aren't recommended since they stick-out and depending upon where you place the printer, may make it easier to run into...
I'd say if you are happy with the printer and print quality, you are fine in simply getting putting in new carts, fire it up and run the auto cleaning from the printer. Don't be afraid to be bold and run multiple cleaning cycles. With your old carts, take them out and give them a good shake and put them back in.
If you know someone with a few old carts they want to get rid of, you should be fine. A couple of the carts I'm using are a couple of years out of date. The worst seems to be the MK which I think is dated 2007. Old carts and ink seem to work just fine in my experience.
Good luck and have fun printing with your 4000!