This is interesting... There is something in the UK (don't know if you have it in the US), called AUtodata. It lists everything you could wish to know about vehicles, including timing intervals and instructions etc.
For the 6VE1 engine after 1998 it quotes 72,000 miles or 96 months. I notice the spec in the knowledgebase says 100,000 miles which did seem high to me. The 6VD1 (3.2) engine is the same unless it is pre-1998 when the stated interval is 54,000 miles or 72 months.
Me thinks I need to change mine!
Be interesting to hear where you all think the differences come from
Nick