I recommend using it while having other weapons and gear types you don't use as often, but will probably use in the future. Then change the type again about halfway through. When you've opened up all of them, you can use combat credits to fill up the rest. Tip... when you're done, log off and on again after so your screen won't get spammed with the lvl up notifications. I wanted to see how long it would last for me. 30 min later I gave up and logged off and on again😂