go into your user CP up at the top of the page

choose "edit options"

go to this

Default Thread View:

and choose from the drop down menu one of these:

Use forum default
Show threads from last day
Show threads from last 2 days
Show threads from last 5 days
Show all threads

i chose shjow all threads to stop it looking as if they have dissappeared on the quieter forums

you can do the same with:

Default Posts per Thread:

and choose however many on a page as you like, eg 20.

it makes browsing the forum a lot easier