I don't know what silo guide you're reading, but I would not nofollow internal links under any circumstance. It's like saying you don't trust or can't vouch for yourself.

I agree with retsek in regard to not putting nofollow on internal links as it may tell an unlikely signal to Google bots. What's more important to trim down in a web page are the duplicate links. Cut repetitive links, either using the same anchors or not, and it will allow you more control on the juices and reputation passing between your site's pages.

but my major doubt it is
When I link a post with the next SILO/CATEGORY, this post is what has been published more recently or is the oldest I've posted?

Don't nofollow your internal links!!