What sawzall blades do you use? Are the expensive blades ($15 per blade) worth buying? I buy the Irwin 10 pack of (medium thickness) metal blades for $13.00. They are the cheapest I can find and I burn through blades quickly. Would a $15 blade last longer, like as long as a 10 pack of cheap blades? Does the saying "you get what you pay for" apply here? And has anyone used the blades that are made specifically for cast iron? if so, reviews?