RMA-ing because of temperature 10 degrees higher? Now in my country that would be the day. RMAs are so strict here locally especially now that they know some people use GPUs for mining. In fact, some computer stores now only give 3 months warranty to GPUs that have been used for mining. I guess if you look sketchy they can simply say your GPU was used for mining then refuse any service or RMA after 3 months has passed.
I'm also from the United States, people get very finicky over just about any and every thing. If something is not operating at optimal performance, then people are likely to RMA their gear. If the warranty is coming to an end, then people are likely to RMA their gear. I have no clue how things work in other countries, but for the most part if the hardware is not operating within 5% of optimal performance there will be an RMA request. Usually the companies have no problem with this, either, but if they believe the damage to be your fault or intentional then they will not grant you a replacement. I've never heard of a warranty that short, but I guess that's a cultural difference for you. Over here, they wouldn't put stipulations such as "if used for mining", because that's an extremely strange restriction to put on your RMA and could be abused as you've already laid out.
It seems the consensus, from the information OP has provided is
exhaust.