I believe the 04+s have the beauty cover covering the individual coils? The newer GM light duty trucks also have the individual coils and short ignition wires design, but they are exposed to moving air and I have not heard of one dying yet. The ones on trucks will well outlast the plugs and wires.

Here's the L92 that goes into Hummers and Escalades, as well as the top trim light duty trucks: notice the individual coils exposed. 5.3 similar.

Just to add something, this was Hyundai's solution:

they made some holes to release heat, but it's ugly in my opinion. Obviously it would be too ugly for a Cadillac. Imagine the Northstar cover with holes.