Maybe it's me and I am getting old.. But since I switch to FF 4 I don't see where I use to be able to tell the program how long I wanted to keep my history for. Am I losing it or am I thinking about something else? ...hope not LOL
Tools>clear recent history is near bottom of list, just above options. I just saw the one for # of days too but now can't remember where. I'll look again.
Stop!!! Careful of that one. I used it fine before but it just got rid of a lot of things. Trying to stop you making a mistake. It has a warning box to let you know you're doing something that cannot be undone.
Some things are gone and need to be put back in, some not. DK
I didn't upgrade to version 4, but the history setting is in Tools--->Options, on the privacy tab in version 3.6.