The post stays around for ever on the blockchain and if you search the title on google it will pop up. However within the categories, posts only hang around for 7 days, you won't notice it in a big category like #photography, because there are hundreds of posts a day to that tag. However if you see a post on there today, it won't be there after 7 days.
Similarly, if you click on #incredibleyou you won't see anything, even though I've written dozens of articles to that category. If you click #cryptogee-musings, you'll see the table of contents, and that is all, however I've done a couple of dozen posts for that as well.
It just means that if you get to an old post and try and find other non-brand new ones, you can't, and that's a great shame I think.
Oh, and the category tag or association tag work just the same, which is why #incredibleyou is empty, if they were as you described (I wish they were), then you'd see all of my articles which have the #incredibleyou tag placed first.