Re: Epson 9880 ver 9800
Kodak recommends every 7 days, and the software that controls the proofer lets you know the last time that it was done. I've gone beyond the 7 days just to see the difference, and after two weeks I could see subtle color shifts, but a client would probably never notice unless they carefully compared both proofs in a viewing booth. So, if your clients are the type that bring a loop to a press check, better stay on top of your calibration.
It's definitely more volatile than our old Veris. I have proofs from almost 4 years ago that print looking identical to a Veris run today, and I never calibrate it manually. The Veris is more expensive to operate and maintain, although the quality is superior to the Epson. The complaint we got with the Veris from our sales team was that it was "too good" and looked better than our press sheets. They wanted a proof that we could improve upon once it was on press, and since more shops are leaning towards the Epson because of price, we followed suit. It's official over here... the inmates are running the asylum!
Seriously, the Epson's make beautiful proofs on a variety of media. Time will tell how much trouble they will be with print head failures and nozzle clogs. We've had our for about 5 months, and so far, so good.