WordPress optimization permalinks structure

Hello,

I wanted to ask you a few questions regarding speed optimization for WordPress.

I am trying to make optimization for my blog prior for launching it. I read the WordPress and there is says that I should use a permalink that starts with a number (i.e. %year%, %post_id% in order to prevent use of verbose rules.

I have a few questions regarding this:

1) Can I use a permalink structure like /%post_id%-%postname%.html in order for WordPress not to create verbose rules. The difference is that I use ‘-‘ instead of ‘/’.

2) I use W3 Total cache plugin.
W3 cache stores static files so it can serve them immediately from the disk. It uses the structure of the path to create the folders. It means that if I have a URL like this:

http://www.domain.com/2011/post.html

W3 Cache will store it in folder called ‘2011/post.html/’ and inside there will be the static HTML file.

The problem is that Linux OS can store approx. 32,000 file in each folder. That means that if I use a URL without like:

http://www.domain.com/post.html

All the static/cached files will be stored in one folder. That means that if I have more than 32,000 posts, there will be a limit for the amount of cached posts that W3 can store.

So my questions is if it is a recommended use (a folder in the URL) for W3 Total cache or I can just use a URL without a folder in my permalink structure?

I need an answer to those two questions before launching my blog.

I use:
Linux Ubuntu 10.xx
Stored on Amazon AWS
Wordpress Version: 3.1.1

Thanks in advance.