Heparin stability in cold OR rooms (ACT accuracy vs heparin activity in Cath Labs)

I'm preparing for my bi-annual Hemochron heparin response correlation study and just received new vials of the heparin used in Cath and CVOR from our pharmacy. I hadn't noticed the storage requirements on heparin before; these vials must stay between 68 and 77 F, which is a very tight range with a very high low end. I know all of our ORs are colder than average room temp. 

I know I am not alone in experiencing Cath Lab questioning ACT results and then questioning heparin activity. I see this coming up over and over on here. I am wondering if heparin storage at cooler temperatures could lead to decreased heparin activity? It would seem an unlikely explanation for the cases of "heparin resistance" we've seen here. I think these cases are likely usually ATIII deficiency and I always put that possibility out there when this comes up but never get any resolution information back from Cath Lab to confirm or deny that.  

TL;DR:
I'm bothered by how close the low end of acceptable storage range for heparin is to room temp (68 F minimum). I could not find any helpful information online about possible heparin degradation when stored at cooler temps.
Anyone have any experience or thoughts on that?