It's both. The ymmv is always big with electronics. I.e. my second last graphics card (gtx970) died within 2 yrs. But the aging effect from running 24/7 under

It's both. The ymmv is always big with electronics. I.e. my second last graphics card (gtx970) died within 2 yrs. But the aging effect from running 24/7 under high load is very real as well. The high temperatures of permanently running on full power just wears it down