45c is good for an overclocked CPU. 55c is what I'd call "the limit" (if you want to push your luck). A 5000+ BE shouldn't make too much heat (but don't quote me on that). When a processor is "rated" for a temperature, that's more like the maximum temperature it will handle before it shuts down. What we're talking about when we say "45c" is more like the maximum temperature you should try to keep it at. The hotter something runs, the shorter it's lifespan is (and the more errors it will produce when stressed). That's not to say that it won't run at 70c, it's just that it shouldn't.