I have compiled my own personal "list" of skin sale info that I've been using for some time now to give me an idea of how long to expect or how often a skin has been on sale.
After discovering your post with the different sale info threads, I thought perhaps other people might benefit from my list.
I don't want to spend a lot of time making a thread that no one will read and that will slip into the "sands of time" so-to-speak. So I'm wondering if it is something you think would be worthy to be on your list of "helpful sale info" links?
Basically I have included information I have found personally useful in a relevant fashion. The list is organized by champion, so that one can see what kind of attention that champion has been receiving from the sales department.
So for every champion, I have the total number of skins that have ever gone on sale, how many times each skin has been on sale, the price of each skin, and the dates the last two skins went on sale -- though this number could be increased to any amount, I have found the last two to be a good indicator of the amount of time a certain champ generally has to wait or how long it will likely be until the next sale.