I understand what Tom is saying. However, it just doesn't jibe with my own personal experiences. That is all. Also, my mother in law does a LOT of baking, and she keeps CAKE YEAST, blocks of it, in the freezer. She gets them from a local commercial baker. I would love to get my hands on some, because her yeast just blooms like crazy. Unfortunately, she's all the way in Canada. Anyways, I was just asking her today about her cake yeast, and how long she stores it for. She says she keeps it in her freezer for up to a year until the original batch is gone, and she has never had problems with her yeast. I've heard, and I must be completely frank that I'm by far not a yeast expert (I just know what I know from my own observations and experiences), that cake yeast is fundamentally a less hardy but more robust version of ADY and IDY. From what I've seen on a Good Eats episode (I know, pretty flimsy source for an opinion, but...), cake yeast is supposedly more delicate but contains much more live yeast than ADY. Alton Brown then says in that particular episode that he never bothers with it since it just doesn't last very long. I really don't take his word, or any others, as the end-all-be-alls. It's just a point of reference for me. Anyways, all I know is, that just doesn't jibe also with what my mother-in-law's experiences with cake yeast has been so far. And she's been using the stuff for over 20 years.
For commercial operations, I agree. It's probably not a good idea to ruin a huge batch of dough with dead or under active yeast. It's probably best to make sure the yeast is fresh and active as possible.
Finally, I think it will not hurt for OP to try a higher water temp. Personally, whenever I try to proof my ADY in 100-105F water, I will not get any foam head action. It just sits there doing f--- all. In fact, I think I'm going to try it again and see. I have a very nice thermapen thermometer that I always use to gauge my proofing water. I'll report back later with details. Maybe I'm wrong here. But, still, for OP, I would suggest he try 120F and see how that helps with proofing yeast. If it's still not producing bubbles or foam head, yeah, his yeast is probably dead.
Oh, definitely cold fermented. I do at least 24 hours, but I often try for 3 days.