I use 2-blade, cut on contact heads. So, I resharpen them and keep hunting. Even if they're bent, I'll try to straighten them out and reuse them. If they'll straighten, fine. If not, they get trashed.

Haven't used replaceable blade heads in ages. I'm a conservationist by nature, so I'm not much of a fan of stuff I can only use once and then throw it away. Except maybe toilet paper.[:-][8D]