Shelf Stable Coffee Mixer

Hello,

I work for a beverage company that has a line of margarita mixes, all fruit based.  

They are looking at launching an Espresso Martini mix product (shelf stable), but it is our first time working with a coffee base.  

So far we have done trial runs, and the product is as follows:

pH - 3.5

BRIX - 18-19

Hot fill - Over 85C 

Cap, invent, held hot for 5-6 minutes, then through the cooling tunnel 

All natural, with some Rowan Berry Extract as that is used in place of Sorbate in our fruit mixers and we have tested this with good results.

They are targeting a 12-14 month shelf life.

I am wondering if anyone has worked with coffee based products like this before? It is our first time, and I would imagine based on our processes, pH etc. Micro won't be an issue (we will test).  I am more curious about off flavours in the coffee down the road, and best ways to prevent these.   

Also, if anyone has any good shelf life testing for products like this, please let me know.

Thank you