By far the highest probability of anything electronic dying is when you turn it on - lots of extra stress on a lot of the components, especially inrush currents in power supplies.
This is the reason some companies tell their employees "leave the computer on", despite the cost of the extra electric usage.
So your suggestion is to underclock the miners during peak hours? Hard to tell what to do, at that price its lots of money to maybe increase life of miners.
Is there an easy way to switch overclock/underclock on a timmer ?