Deep Autosave/Revision History

I’m really trying to understand versioning and backups. What I want is to have access to a deep history of page changes. Ideally this could be managed so the saves are very frequent, only triggered by actual changes, and stored in such a way that only representative instances are preserved from longer ago.

I’m so frustrated with the autosave function, in the way I’ve encountered it. It may be that I just don’t understand it well or know how to use it properly. It’s saved me a few times when I catch the need to roll back very quickly, in the same editing session – but the times I’ve needed it most, like when discovering upon returning to a page that’s already been saved after some time, and discovering that on last editing some major unintended change had occurred, in that case I come up empty.

I understand that the default function saves to the database, and for this reason people and plugins seem more concerned with limiting the versions saved, rather than extending them. But why does this have to be, and are there alternatives?

1) Are autosaves and revisions the same thing, or different? If different, are all saved to the database? What’s the difference, and how to access these settings and saved versions?

2) How are you supposed to access revisions older than a few minutes? The talk of limiting saved versions makes me think it can be set up somehow so as to save enough versions to have to worry about limiting them, but I can never seem to find any way to access more than 2 or 3 very recent revisions.

3) Are there any GOOD plugins out there for any of the functionality I want?
* Ability to save many versions without clogging the database (maybe stored elsewhere)
* Ability to save frequently, to preserve small edits during a work session
* Ability to limit what is saved from the deeper past in the way many backup systems do, by saving only representative instances, less the longer ago the save, but not deleting all further past saves based on absolute age or number of saves allowed. (this creates the need to choose between no deep history, or infrequent save intervals)

4) Failing that can anyone suggest a workaround or practice that could fulfill any parts of this function?

Thanks for any help or suggestions