I post this here just if anyone comes asking.
I thought I was going crazy because pages I have visited were going vanishing... and it's a new feature by Mozilla... yay!!!!
For those that don't want to read it, basically says that the history is expired dynamically and as if that wasn't enough, depeding on your system specs it happens even in a sorter time period. Me, used for a 2 months time that is... oh my god. I visit loads of different pages in just a couple of days!!! And I want to keep them!!!. Remove the history dynamically is crazy!!!
I don't know who the hell at Mozilla thought that can decide by me if I want to keep history or not, if I want "privacy" or not, but should be hanged. [rant off]
As a workaround, you can set the pref places.history.expiration.max_pages to a huge number.
As well, if some with dev skills can port this Firefox Add-on to K-meleon, will be great.
Anyway, it says that set the above pref too high will decrease performance... Maybe, just, maybe is true, but... what about not using sqlite database for keep history. Didn't they thought about it in Mozilla first?