In firefox if you put “about:config” in the address bar and hit enter you will get a configuration page after they warn you. To filter out the irrelevant options type “history” in the filter box. I believe the option you want to change is “browser.sessionhistory.max_entries” to something greater than 50. I haven’t verified that this will achieve what you are looking for though. Do you want the physical box to be larger so you don’t have to scroll as much or do you just want more items listed?
Edit: What I just suggested will increase how far you can go back or forward with the back or forward buttons. JC we need your help!
If you go into the preferences and make your history cover a longer period, the dropdown should have more data to draw from to create that selction from.