Current C41 and E6 technology, in accelerated dark testing(what ever that means) is claiming 100 year dark storage life, in the real world it will come down to how many times it is exposed to light, which can cause the dyes to fade on the emulsion, in the store I worked in, we used several slides in a sleeve to show a light table off, and there was noticable fade in the slides after only a couple of years. Of course with C41 it will depend on how many times you used the neg to make prints, as each time you do, it is exposed to the light from the enlarger, but even with some fade, you can correct the fade in the neg with color correcting filters.
Originally Posted by snaggs
As far as keeping K process films alive, this, at least in the US would be a long uphill battle for a couple of reasons, 1. It is a highly caustic process to develope it, and most states will not allow the enviormental impact it can cause... 2. The general public at large, will no longer wait for days or weeks to get there slides back from the processor, in the world of 1 hour labs and digital instant gratification, you can't tell them it will be a week to get their stuff done, and unfortunately the bottom line to the big company is volume and not the specialized market such as us.