I think it depends on the temperature and humidity where the printer lives. I was away and my 3880 sat idle (and powered on) for two weeks. When I did a nozzle check today, there were a bunch of missing nozzles. A single cleaning was enough to bring them back.
I think "powered on" is the problem here. The one time I had a nozzle clog on my 3800 was when I left it powered on for a couple of weeks without making a print. Took several cleaning cycles to fix. As long as I shut the power off, I can leave it for months without printing, no clogs, no problem. Great printer.
Keep in mind that the 3880 will NOT print borderless on 17 by 25. The 4xxx series will not print borderless on any size of cut sheets.
This may be a reason to have both printers. One of my colleagues does, so she can print production stuff on roll paper, and small cards and cut sheets on the 3800.