Does optimum re-ranking take effect immediately after being spidered?

[hulahoop]

Hello,

I have pretty good rankings now and don't want to upset it but improve it. I have re-optimized my page and want to know how search engines especially google work...

Example:
I am ranked 11th place on keyword 'X'.
If I upload my new optimized page, once it is spidered, will I be able to get to the deserved spot (say 2nd place) immediately. OR will it take several spidered times to take effect.

If no, how do you advise I do it? In phases?
Basically I am afraid to lose my ranking.
Please advise.

[hulahoop]

Really need to know if changes will take some time to take effect? Let's say I am suppose to yet 2 ranking, does that mean I immediately jump from spot 11 to 2 or does it take some time to take effect.

Need to know as want to be sure not to mess my ranking. Also need some indication if what I have done is right and if not, when do I start to optimize again?

[rfung]

From what I read, it takes some time from the time you get spidered and the time the changes get reflected in the rankings.

[hulahoop]

But does it mean once the spiders go through the site, it should reflect the optimum result for that 'at that moment optimization'?