CS>Polarity reversal

[Gm Gm]

Hi there:
           Just wondering if anyone has done any experimenting with the
timing for polarity reversal. Not doubting the 1 minute at all. But at that
rate, that would be 60 cycles an hour, and 600 cycles for a 10 hour brew.
Since I make several brews at a time, that is a lot of wear and tear on the
relays. Does anyone know the lifetime cycles those relays can handle before
failure? I am going to be using a DH 48S-2Z unit from Amazon.
   Thank you... Regards Grant.