I now have a Duron 1GHz that I OC'ed to 1.33 and you can see its results
here. It's using PC133, so it is somewhere in the ballpark of your 1200MHz system, and it would be doing about 5 WUs per day if I just used it for browsing and normal stuff. When gaming, I generally switch SETI off because it really doesn't get anything done when I'm gaming, and so my WU times are abnormally long.
On that page, note the column marked "AR," which stands for "Angle Range." Work units recorded at a high angle range, where that value is above 1.0, complete relatively fast, while 0.4-0.5 is "typical" and less than ~0.05 is the dreaded VLAR (very low angle-range) which are extra tough and chewy. So the WU speeds are going to depend somewhat on the angle range.
One utility I always like is SETISpy, because it gives some interesting info about the work unit, the system performance, and tells what the AR is. You can put SETISpy in the same folder as SETIDriver, then click the "Use SETI Spy" checkbox and start SETISpy. It will report on the current WU. You can get SETISpy from
here.
edit: I should mention that the WUs with times above 7 hours are from previous rig, a dual-Pentium3 733 system. And the stats page you're seeing there is an example of a SETI Que, which you can join (look at the sticky thread up top).