Re-rendering of avatars and prims. Why? Improvement suguestion?

One of my pet peeves is the system’s need to re-render avatars and objects just because you changed the direction of your view for 15 seconds and returned it back to where it was. (Even my own avatar will sometimes be missing parts and I have to wait 5 to 10 seconds for it to fully be restored. I’ve set my cache to the max 1Gig. And my system ram is 1Gig; also my video ram is 256Meg. So why Am I seeing this phenomenon? I spend most of my time at one place, (Furnation), which is also visited by many of the same people. Is there really so much data that it can’t be cashed? Also when I quit SL and then restart it, why does it have to download everything again?

I know some cashing is being done already but i don't know what it is cashing. May be the following in some form is being done already. This is what I had in mind, which may help reduce these annoyances. It would seem to me you could treat all prims like web site cookies. Have a last edited or expire date stamp embedded in them. When the client side starts to render a location it will receive from the server the name and date stamps of everything to render with in the visual range. The client side will then decide if there is any new prims and also if there is a need to updated any of the prims in its cashe and will request the data from the server. Frequently rendered objects would be kept on the client side local drive for use on the next visit, (drive letter and folder settable/changeable by the user). This way only new data will need to be sent from the server, which will reduce bandwidth load and provide faster rendering. This may require steeper hard drive requirements for the program but if it speeds up rendering time and reduces the frequency of the need to re-render prims and avatars, I feel it will be welcome.