Weapons Spree for the Long War

This article from Spacewar asks the question, if the Pentagon is committed to fighting "extemism" in the Long War, why are we still buying expensive legacy weapons?

There are two possible explanations. The first is that big and expensive defense-equipment programs (combat aircraft, naval destroyers and submarines, missile defense) continue to be built at escalating costs -- $84 billion for 2007, 17 percent more than planned, and 15 times the cost of Special Operations Forces -- despite being more suitable for traditional wars than for fighting dispersed terrorists.
The contractors and military services wedded to these huge investments will claim that every dollar is essential for fighting al-Qaida...

And the other reason has a point:

the Defense Department has its eye on one especially formidable potential opponent: China. In fact, China is investing heavily in missiles and submarines, precisely the weapons that would make U.S. forces vulnerable in the Western Pacific.

I guess its the old adage of "better safe than sorry', but how long can we keep this up plus social programs and not end up like the Soviet Union.