Hello, Pebkac, and welcome to the DMT Nexus!
It sounds like you're in a hurry and still have much research to do. Ayahuasca isn't something to rush into.
Here's a link that gives a good overview all about ayahuasca. This thread should answer your questions about cooking times, water acidity, types of water, and gives an overview about foods to avoid. I recommend reading the whole thread, as it has a lot of other useful information that will help you during the journey.
As for the shelf-life of your plants, I'm not too sure. Your question has probably been answered previously. Doing a thorough search of the forum should help you find the information you're seeking. If not, posting a new thread with a more specific title such as "Caapi and Mimosa Hostiilis shelf life?" should get more people's attention.
Good luck to you and your gf on your journey!