Soooo, I actually did an experiment with some old pens I had from before I went on the pump. I left them in my purse and watched to see what would happen. Mind you, I never actually used the pens. After about 6 months of leaving the pens in my purse they started to get cloudy (Sep-Mar). I live in Maryland, our weather fluctuates so much so we never consistently have very hot days in the summer or consistent cold days in the winter. Now because this summer has been a bit hotter than normal here I've seen that in recent months they have become even more cloudy and seem to be clouding up faster then they did in the winter, which makes sense!
I don't see a problem if you are keeping it in the fridge most of the time, if it's in the heat for a few days I don't know how I'd feel about using it. A prolonged exposure to the heat is going to make it less effective, but like i said if you're putting it in the fridge every night or something I think you should be okay.