I ran out because I like to upgrade everything I get and give it a shot, also because I've been trying to improve all the weapons I've been holding on to and infusing them costs parts too. People who mainly enjoy PvP don't get many weapons. Hell I got 4 guns from arms day and to infuse and upgrade those will cost me a healthy chunk of parts. 10 per for infusion and another 30 or 40 for the upgrades. I find myself in need of a few hundred parts just for those.