It is important to make application as light as it can. First impression is always a great deal. People will leaving if the process take too long and not good for user experience.
The Flash Player cache is a new feature available in Flash Player 9 Update 3 (9,0,115,0). The cache allows files signed by Adobe to be cached by Flash Player. These files end in the file extension .swz.

The Flash Player cache differs from the browser cache in some useful ways. Because the cached SWZ files are signed by Adobe, they can be reused in more than one domain and are not limited to reuse within the domain in which they originated. For example, imagine that framework.swz is loaded from http://www.a.com and is placed in the cache of Flash Player. If the same framework.swz file needs to be downloaded from http://www.b.com, Flash Player looks in its cache to find a.com’s framework.swz file. When it finds a match, it uses the cached file rather than loading a new file from b.com.

The SWZ file persists in the cache even after the browser is closed. The file remains in the cache indefinitely, provided that the end user does not change settings in the Flash Player Settings Manager to reduce their caching ability. However, future SWZ files may eventually cause older, unused SWZ files to cycle out of the cache when the cache size limit is reached.

Fortunately, you need only one copy of a framework, since Flash Player uses a common cache for all browsers on a system. This means that if a user downloads a SWZ file using Microsoft Internet Explorer, that same SWZ file will also be available in Mozilla Firefox.

Read it more at http://www.adobe.com/devnet/flex/articles/flash_player_cache_print.html