It can take anywhere from just a few minutes to ~an hour. What it does is nothing revolutionary; at least not to your everyday programmer. Any software that uses databases, which FF does, as well as some of it's extensions, (SQLITE database(s) in FF's case) will generally benefit by compacting / defragging the database(s) after they've been in use for a while. They can get bloated and full of 'junk' just like your regular computer after awhile, which (hopefully) you also run a defragger on once in a while. (You do don't you? ).

So that's what Speedyfox does, it just optimizes and compacts any SQLITE database(s) it finds regarding FF, which can have some impact on speed if they've gotten messy enough over time. Here's a snippet from their website:

I ran it on mine, and while I can't really say that I got that 'newly installed' feel, (since I also run a staggering amount of extensions as well), it certainly doesn't hurt anything (read: generally very safe to do), and it's nice knowing I've done some tweakage.

Give it a shot and let us know if you got that fresh, newly installed feel.

Download it HERE