I agree, there is a lot that can wrong, but there also seems to be a lot of stability in the process (but my experience in E-6 is only with the Tetenal 3-bath). For instance, unintentionally once I mixed the 500ml kit as if it were a 1-liter kit. Fortunately, I figured this out before running film through it. But, being the tightwad I am, I processed some film through it anyway, extending the time (I can't remember the exact increase, but I don't believe it was simply doubling the normal time) and lo and behold, no noticeable difference in density, color, or contrast from other proper developments. (I shoot mostly scenics and architecture, so maybe color is not as critical as say portraiture). Another time I pre-soaked the transparency film (EGAD!) which is what I do with my B&W film (sometimes I'm like a robot in my dark-closet). Realizing that I'd "swelled" the emulsion with water, I simply WAG'd that I'd need a little more development time, so I added about 15secs more and presto, no noticeable difference. Hmmm, lots of variables. But lots of fun, too.