In an absolute sense, higher temps will cut down VRM lifetimes as well as add a few watts to your power usage (higher temps = higher leakage current = lower efficiency). However, a couple of things mitigate this a bit. The circuitry is designed to work at high temps, efficiencies have gone up (less waste heat = less self heating), and in general mobos are being designed with better heatsinks/heatpipes.
That said, I prefer some airflow over the VRM heatsinks if possible. Either via case fans (especially for liquid coolers) or a tower fan that drops down below the cooler's fin stack a little bit. Look for mobo's that don't skimp on the VRM cooling.
...and most of all, don't buy VRMs made out of pork products.
Quote:
..the boars practical life..