Well, lets see if I can make it clearer. I can set up a scene, it can take me hours to do so, and in most cases I can render in a half hour or less. Usually the time is dependant on the number of lights, and how drastic the shadows are etc.

I can then save the scene, reload it at another time, try to make alterations. In today's case I removed the fog from the scene as I wanted to postwork the fog into the image. When I went to render the scene, it had to optimize the scene first. I went from no optimization to 14 frames that needed to be optimized before it could render. In irritation I saved the file, dropped out of studio and reloaded the scene. The second time, it had to optimize again, this time with 28 frames. Now the main reason for my irritation is that studio has been known to occasionaly crash out when the optimization get's too awfully drastic. In a complex scene, I might expect that, since I'm not running a super computer. In a small scene such as today and yesterday's render, I do not expect that. And I certainly do not expect the scene to be altered in any way from the original, unless I make significant alterations.
I guess I am confused about what studio is doing with the scenes, that causes them to need to be optimized after I reload. *shrugs, I couldn't claim to be an expert on computers, let alone studio. It can be an extremely stable program under all but the most unusual circumstances. However, if I haven't made significant changes in the scene, have rebooted my machine and studio from scratch, I would expect the scene to render as flawlessly as it did the first time. Short of some unknown issue that only a programmer might understand.
Anyhow, I hope that claifies things. And perhaps you have the understanding regarding studio that I lack. And I appreciate you taking the time to reply to my question.

Mark