It depends on how you store your fuel and what you are trying to accomplish.
If you can keep the sun off your tank by putting it in a building, under a roof, or underground your tank will stay a lot cooler. Temperature seems to be the primary problem if you use cetane enhancers.
The length of time you store your fuel is also a factor. No one can give you an exact length of time because so many other factors effect this, such as humidity, fuel age when delivered, make-up of the fuel you get, and temperature. In general it seems storing fuel more than six months means you really need a stabilizer, and you probably should avoid cetane enhancers.
Are you really looking for a cetane enhancer? Or are you more concerned about fuel stabilization? The point I've been trying to make is...not all fuel treatments are the same. They do different things. Don't use the wrong product to do a job that it wasn't made for. It may actually be working against your goal.
If you are looking for a stabilizer, take a look at
PRI-D. You will also need a biocide, PRI makes one too.
Despite a number of people saying that they are going to keep using PS in their storage tanks no matter what, I haven't seen any published material that this makes sense in all cases. I have read documents saying it could be a problem. I know enough about the chemistry here to that I'm not reading BS. Companies like Chevron have no reason to argue one way or the other. They are just providing information.