If the OP is considering a 2002 V6. If the fact and proof that the oil wasn't change on a regular bases, I would pass. If synthetic oil was used, there will NO sludge problem.
The 2.4 since I have a 2004 RAV , 124,000 miles, with the 2.4 engine and the vehicle was built in late 2003 I follow the head bolt problem. In my opinion, until my vehicle is junked the potential will always be there. A $440 kit and 3 days for a DIY repair, if need arises.
I also have a 2001 Avalon V6 with the known sludge problem and use synthetic oil as I did with the 97 V6 Camry before that. So no problem for me.