Apology accepted
Ash I think the answer is that there is such a variation in shelf-life of diluted products. You've hit upon one varying factor which is temperature, but a large factor may be the water you used to dilute them with!
For example, a colloidal product mixed with hard water will start to "clean" the mineral deposits in the water - I live in a hard water area myself and when I mix m-power with tap water it gets a white scummy deposit in it. I would always mix up something like that fresh every time, or at the very outside use nothing older than yesterday's mix.
Diluting a product into a container will no doubt mean that you've got lots of bacteria and microbes mixed in there. At raw strength most products would probably inhibit any growth of life-forms but once you dilute them down the micro-organisms would almost definitely find it easier to start growing.
I think most "conventional" detergent chems would have a very long shelf life mixed up, to be honest. After all they're full of stuff like preservatives.
I would hazard a guess that some of the "Eco" products that proudly boast not to contain lots of things might not enjoy such a long shelf life.
Interesting question though
