Thank you for your reply. Wondering is there anyway to test the ambient-stability of a product?
Most likely way to find out is to try it. If you don't have heated cabinets or similar, there are various external labs that will be able to provide this as part of accelerated shelf-life testing services.
As for the broker, ideally you want your container down in the hold where it is less exposed, but you'll want to approach with a degree of scepticism about any claims they may make on this, IMEX - quite a few will say that they will "try to" arrange this, but unless they put a lot of volume through the shipping lines they are rarely able to guarantee it, as the scale of container shipping is so vast that they don't want/need to have the flexibility to accommodate oddities unless there is actual significant commercial justification for it.
Understanding the journey length and route is also very useful, so you should certainly ask about that. Keep in mind that there can be delays, and if you ship frequently enough then you'll definitely encounter these 