How long have people used installed carts past the 6 months? I'm not a heavy printer, and there's no way I will use up a set of 3800 carts in six months.
I bought my 3800 in November 2006, it was one of the first available in the UK, and it still has three of the original carts installed.
I pulled them all out last year when changing a cart and gave them all a shake, but I've not noticed any deterioration in print quality since new. I rather hope that the automatic agitation technology Epson boasted of when first launched the 3800 has a lot to do with it.
I've also only ever had one nozzle clog after a particularly heavy head strike on some thick art paper in the first week of use.
If I was bothered could go back to the original profiling targets I printed and compare them with a new set.
I've also got a 2100, again an early one into the UK, and some of the carts still in there are well beyond their use by dates now and all worked well when it was last switched on.
So in my experience keeping carts beyond the six months date is absolutely no problem at all.
All the printer are kept in normal domestic UK conditions.