Loader Cache

So, I heard that when loading an external swf Flash automatically keeps a cache. I’ve seen this behavior a lot of times, but I wasn’t completely sure.

My question is: up to where is a good idea to trust this cache?

I’ve this kinda complex system that ends up loading the same two swfs (for interface and font) more than once everytime it’s fired, and was wondering if I should optimize it to load only once or leave it to the cache.