Simple, just buy a computer with a larger screen Sick..duhhh.. User control panel=Edit Options=bottom third of page.
Go to User CP which is linked in the header .Then on the left hand column go to Edit Options . Then go to Number of Posts to Show Per Page Use this option to set the number of posts to show in a thread before splitting the display into multiple pages. Use Forum Default ,Show 5 Posts Per Page, Show 10 Posts Per Page ,Show 20 Posts Per Page ,Show 30 Posts Per Page, Show 40 Posts Per Page -Hope that is helpfull . While you are at it there are many other options you can take a look at too .