[nnkh]

The same thing you do with RSS/Atom feeds. They don’t magically disappear unless they’re deleted. If you mean you think they would get buried under regular human tweets, you can make a list. I have a news list for this.

[Touche]

They do disappear off of your feed in which case you'll never see them again. There is no concept of "unread" tweets, like there is with RSS.

[nnkh]

You can scroll down. The latter is true.

[Touche]

> You can scroll down.

Not if you check it once a day (or even once an hour depending on how many things you follow), it's gone by then.