No, so long as you can turn a WU in six days you are in like Sven. I turn one every day, and the server turns one every day and a half, and a dual core 1.6Ghz laptop turns one every two and a half. Mebey I will add another couple to the SMP.
They actually seem to run 4-6 degrees cooler with the SMP client that two large WU clients running, just make sure that you have enough RAM to handle it. The four running instances took a bit over 1GB of RAM on my system at work.