There is NOT a TSB for the sludge (engine gelling). There is a special policy adjustment (SPA) that covers Sienna, Camry and Avalons. As a Toyota technician (8 yrs), I have NEVER EVER seen a sluged engine on a vehicle that had the oil changed at a resonable interval. Toyota, in my opinion, has really gone out of it's way to help people with the problem, even though it is poor maintainence that causes the problem in the first place. I have done many of the sludge repairs, and the majority of them have had around 1 oil change per 15,000 miles. Several engines that I have done had 2 oil changes in 60,000 miles. A lot of the customers bring in their oil change receipts, and admit that they have only done a few oil changes.
I've seen a lot of 2nd owner vehicles come in comsuming oil and smoking. The owner doesn't really know the oil change history, and Toyota occassionally denies the repair.
Bottom line, change your oil, and you won't have to worry about sludge.