Um...also a random question. Why are there so many bottles in this photo??
I don't have personal knowledge of the Tetenal kit, but typically C-41 developer would come as 3 separate liquids (called part A, B, and C). Usually this mix is technically developer REPLENISHER, and another part, called "starter solution" would be used to help convert it into actual processing tank solution - what most photogs would simply call "developer." In some small kits, it is already in the form of "developer" (as opposed to replenisher), so no additional "starter" is needed. Anyway, this should help to explain why so many bottles.
I'm used to my b/w chems lasting a really long time (often used past recommendation) so "two weeks" surprised me quite a bit.
B&W developers are typically able to use as much "preservative" (commonly sodium sulfite) as they wish, so they can have very long lifespans. Color developers, like C-41, are a different animal. During development of C-41 film, sulfite actually prevents formation of the colored dyes, so in a working developer, sulfite has to be kept at a very low concentration. This minimal quantity of preservative helps lead to the short service life. Storing in glass, with no air space, will help keep it there as long as possible.
There IS another way to greatly extend the lifespan of C-41 developer. One can use what is essentially a "slow drip transfusion" for the developer, restoring individual chemical components to the proper working level. At first, this sounds like a far-fetched idea - something you would never be able to do. But, as it turns out, this is the basic idea behind replenisher, as in the first paragraph. Other problems come along with replenishment, so most small users probably don't want to bother. But just saying, this is how it works.
