BUT... I probably would print with it in fits and spurts -- printing most weekends and even week nights during a spurt and then letting it sit idle for a month or more. According to the internet, that leads to clogs. I'm wondering if there is a way to properly mothball the 9900 if I know I'm not going to print for a month or perhaps even several months. Or... I could rig up a cron job to print a 4x5 card every N days during the idle period. Or ... ?
Here is some empirical feedback:
I have had a 7900 for about 4 years now. Like you, I print in "fits and spurts" - sometimes going for several weeks without printing.
In those "down" periods, I run a quick nozzle-check on a plain 8.5x11 sheet once a week (to push at least some ink through it - knowing that Epson has a reputation for clogging). Though there are times I don't even do that.
Most of the time the printer does not clog. But, on the occasions when it does, I've found that cleaning does work. There have been a couple of times that I have had to use the "power clean" routine. Before each printing session, I do run a nozzle-check.
Do I worry about clogging? Yeah. Is it a hassle to deal with the occasional clog? A little. Would I prefer Canon's apparent superiority re: not-clogging? Sure, why not.
Personally, although I am technically inclined, I'm not that interested in head-and-printer-internals design, and debates about the merits of each vendor's design approach (although I certainly don't mind you guys doing it among yourselves - have at it). I just want the dang thing to print when I'm ready to print.
So I am more concerned about empirical performance.
All-in-all: the prints look great, I've gotten my money back by not having to go outside for prints (got the printer for a good price), I enjoy having print control in my little lab and (so far/ fingers-crossed) the printer hasn't died with a terminal-clog. What's not to like?