Looking at the size of the cultures.. each one should last about 3 months (unless it crashes for some reason). Towards the end of the 3 months, if you see the media drying out (dry larvae tunnels), you can add very small amounts of water to freshen it up and it should hold long enough for the very last of the larvae in that culture to finish growing large enough to pupate.
Now, unless you have a ton of small herps or inverts to feed the fruit flies to, you should try to stagger the making of your new cultures. Make one new culture one week... wait 2 or 3 weeks (depending on how many animals you are feeding) and then make a second new culture, and so on. If you make a bunch of new cultures at one time, you are just going to wind up with millions of flies from all cultures at one time and no where to put them. As you found out, just because you removed the flies from the original culture to make new cultures doesn't mean you won't get any new flies from that original culture... the larvae are numerous and continue to develop and pupate into new flies.
I typically don't like the natural colored media as it can be difficult to see how many larvae you have until they are almost large enough and ready to pupate. I normally use the standard blue media from carolina biological and only use natural colored media when I have nothing else. If all I have is natural media then I'll add blue or green food coloring to the water before I add it to the dry media mix.. so that it helps make it easier to see the smaller larvae... off course the food coloring method makes the media look a bit gross (as it's not a true bright color) compared to the pre-colored types of media but it works for me.
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PHWyvern
