[Kungpow]

I have a GBB King Arms M4 and AGM M4. I found that the components in the trigger housing get the most wear. With the AGM M4 the sear will be the first to wear out, then the trigger and hammer. The bolt catch may wear over time, however, it is the edge of the bolt carrier that gets rounded off.

I believe the G&P Challenge kits use cast aluminum parts (Better than the King Arms and AGM Zinc Alloy parts) so they will be more durable over time.

Personally, I think you should use it until something breaks, then get a set of replacement parts.