Curious question... Which plug breaks down faster? The Med Cold or Med Hot?

I have burned through 4 Med Cold/Cold plugs in the past 3 months.

I was doing some tuning and testing with the truck, so that may be the cause of one. I have run Med Hot plugs and one would last months. I was running the HPI R4 and R5, but now I am going to shift to HPI R3's...