What
Some time ago, Congress made certain changes to the estate taxes. As a result of the changes, effective January, 2004, the tax free amount increased to $1,500,000. (Back in 1997 it was $600,000.) This allows a married couple to leave a minimum of $3,000,000 tax free.
Your Living Trust does not need to be changed to incorporate these changes.
However, there are other developments which might be appropriate to consider.
1) You might want to consider a Dynasty Living Trust. The advantage of using the generation skipping tax exemption is greater during the grantor