You're right. Perhaps I was unclear. They're expensive CPU-wise to make but it's trivial from a user interface perspective/ user interaction perspective to re-make them. Its bad that we have to spend the CPU but its not a huge inconvenience or error. As with all caching its not a big deal if we dont have a cached version since we can get the "original" and cache it but the purpose of the cache is to not have to get the original every time.