Idle at 35-45C is high, even with the stock HSF. Granted there are a lot of variables such as: airflow, cable management, ambient temps. The last is one of the biggest factors, what is the temp air around the computer? My i7 860 idled with the stock HSF at +7 over ambient. I would expect an idling i5 750 to produce less heat.
And 72.7C is an awfully specific number. Where did that come from? The full load safe max is likely much higher than that and you would expect to see your CPU throttling itself as it tried to deal with the stress as it approached its thermal envelope. Now certainly staying under 75C can be a good goal, it depends what your aims are.
My i7 860 under full load went over 80C. I don't load it up that often but I wasn't happy with those temps so I replaced the stock HSF with a CM Hyper 212+. Problem solved. My CPU now idles at or just above ambient temps and last time I checked it under full load it was at 51C, which was 33C over ambient.