I have been making dairy-free chocolates for a few years now.  I've experimented with canned coconut milk (and coconut cream), coconut oil and other nondairy milks for making ganaches.  I haven't noticed any difference in shelf life from when I made dairy ganaches to now using canned coconut milk and/or coconut oil.  I've always considered the shelf life to be about a month.  You need to consider the water content of whatever nondairy substitute you are using to help you think about the shelf life.  The higher the water content (water activity), the shorter the shelf life.  I have not used agave as a sweetener, but I'm wondering if you can think of it like glucose which can actually stabilize your product and extend its shelf life.  I found this website with specific information about agave being used as a stabilizer.  Go to: http://www.international-organics.com/info-files/Intl_Organics_Organic_Agave_Info.pdf

Hope you find success with your dairy-free chocolates. 

I am making a dairy free ganache, replacing the cream with coconut cream and the butter with coconut oil. Will this make my ganache have a shorter shelf life? Any idea of what the shelf life will be? Also, I'm using agave syrup as my sweetner- will this alter the shelf life since it is a wet sugar, so in turn adding more liquid to teh recipe?

Thanks!